2000 Nonemployee Director Stock Option Plan

EXHIBIT 10.15

KIRBY CORPORATION

2000 NONEMPLOYEE DIRECTOR STOCK OPTION PLAN

ARTICLE I. GENERAL

     Section 1.1. Purpose. The purpose of this Plan is to advance the interests of Kirby Corporation, a Nevada corporation (the “Company”), by providing an additional incentive to attract and retain qualified and competent directors, upon whose efforts and judgment the success of the Company is largely dependent, through the encouragement of stock ownership in the Company by such persons.

     Section 1.2. Definitions. As used herein, the following terms shall have the meaning indicated:

     (a) “Board” means the Board of Directors of the Company.

     (b) “Change in Control” means the occurrence of any of the following events:

     (i) Any “person” (as such term is used in Sections 13(d) and 14(d)(2) of the Securities Exchange Act of 1934, as amended) becomes the beneficial owner, directly or indirectly, of voting securities representing thirty percent (30%) or more of the combined voting power of the Company’s then outstanding voting securities or, if a person is the beneficial owner, directly or indirectly, of voting securities representing thirty percent (30%) or more of the combined voting power of the Company’s outstanding voting securities as of the date the particular Option is granted, such person becomes the beneficial owner, directly or indirectly, of additional voting securities representing ten percent (10%) or more of the combined voting power of the Company’s then outstanding voting securities;

     (ii) During any period of twelve (12) months, individuals who at the beginning of such period constitute the Board cease for any reason to constitute a majority of the Directors unless the election, or the nomination for election by the Company’s stockholders, of each new Director was approved by a vote of at least a majority of the Directors then still in office who were Directors at the beginning of the period;

     (iii) The stockholders of the Company approve (A) any consolidation or merger of the Company or any Subsidiary that results in the holders of the Company’s voting securities immediately prior to the consolidation or merger having (directly or indirectly) less than a majority ownership interest in the outstanding voting securities of the surviving entity immediately after the consolidation or merger, (B) any sale, lease, exchange or other transfer (in one transaction or a series of related transactions) of all or substantially all of the assets of the Company or (C) any plan or proposal for the liquidation or dissolution of the Company;

     (iv) The stockholders of the Company accept a share exchange, with the result that stockholders of the Company immediately before such share exchange do not own,

immediately following such share exchange, at least a majority of the voting securities of the entity resulting from such share exchange in substantially the same proportion as their ownership of the voting securities outstanding immediately before such share exchange; or

     (v) Any tender or exchange offer is made to acquire thirty percent (30%) or more of the voting securities of the Company, other than an offer made by the Company, and shares are acquired pursuant to that offer.

For purposes of this definition, the term “voting securities” means equity securities, or securities that are convertible or exchangeable into equity securities, that have the right to vote generally in the election of Directors.

     (c) “Code” means the Internal Revenue Code of 1986, as amended.

     (d) “Committee” means the Compensation Committee, if any, appointed by the Board.

     (e) “Compensation Plan” means the written plan or program in effect from time to time, as approved by the Board, which sets forth the compensation to be paid to Eligible Directors.

     (f) “Date of Grant” means the date on which an Option or Restricted Stock is granted to an Eligible Director.

     (g) “Director” means a member of the Board.

     (h) “Eligible Director” means a Director who is not an employee of the Company or a Subsidiary.

     (i) “Existing Plan” means the 2000 Nonemployee Director Stock Option Plan, as amended by the Board on January 27, 2004 and approved by the stockholders of the Company on April 27, 2004.

     (j) “Fair Market Value” of a Share means the closing price on the New York Stock Exchange on the day of reference. If the Shares are not listed for trading on the New York Stock Exchange, the Fair Market Value on the date of reference shall be determined by any fair and reasonable means prescribed by the Committee.

     (k) “Nonincentive Stock Option” means an option that is not an incentive stock option as defined in Section 422 of the Internal Revenue Code of 1986, as amended.

     (l) “Option” means any option granted under this Plan.

     (m) “Optionee” means a person to whom a stock option is granted under this Plan or any successor to the rights of such person under this Plan by reason of the death of such person.

     (n) “Payment Date” means the last day of a calendar quarter.

     (o) “Plan” means this 2000 Nonemployee Director Stock Option Plan for Kirby Corporation, as amended from time to time.

     (p) “Restricted Stock” means Shares granted under this Plan that are subject to restrictions described in Article III and the Compensation Plan.

     (q) “Share” means a share of the common stock, par value ten cents ($0.10) per share, of the Company.

     (r) “Subsidiary” means any corporation (other than the Company) in any unbroken chain of corporations beginning with the Company if, at the time of the granting of the Option, each of the corporations other than the last corporation in the unbroken chain owns stock possessing 50% or more of the total combined voting power of all classes of stock in one of the other corporations in such chain.

     Section 1.3. Total Shares. The maximum number of Shares that may be issued under this Plan shall be SIX HUNDRED THOUSAND (600,000) Shares from Shares held in the Company’s treasury. If any Option granted under the Plan shall terminate, expire or be cancelled or surrendered as to any Shares, new Options may thereafter be granted covering such Shares or such Shares may thereafter be issued as Restricted Stock.

ARTICLE II. STOCK OPTIONS

     Section 2.1. Automatic Grant of Options. Options shall automatically be granted to Eligible Directors as provided in Sections 2.2, 2.3 and 2.4. All Options shall be Nonincentive Stock Options. Each Option shall be evidenced by an option agreement containing such terms deemed necessary or desirable by the Committee that are not inconsistent with the Plan or any applicable law. Neither the Plan nor any Option shall confer upon any person any right to continue to serve as a Director.

     Section 2.2. Automatic One-Time Grant. Each Eligible Director shall automatically be granted an Option for TEN THOUSAND (10,000) Shares on the date of such Eligible Director’s first election as a Director.

     Section 2.3. Automatic Annual Grants. Immediately after each annual meeting of stockholders of the Company, each Eligible Director shall automatically be granted an Option for SIX THOUSAND (6,000) Shares.

     Section 2.4. Election to Receive Options. If the Compensation Plan permits Eligible Directors to elect to receive an Option in lieu of all or part of Director fees otherwise payable in cash, each Eligible Director who has properly and timely made such election as provided in the Compensation Plan shall automatically be granted an Option for a number of Shares equal to (i) the amount of the fee such Eligible Director elects to receive in the form of an Option divided by (ii) the Fair Market Value of a Share on the Date of Grant multiplied by (iii) 3, with the result rounded to the nearest whole Share.

     Section 2.5. Option Price. The option price per Share for any Option shall be the Fair Market Value on the Date of Grant.

     Section 2.6. Date of Grant.

     (a) The Date of Grant of an Option granted under Section 2.2 shall be the date of the Eligible Director’s first election as a Director.

     (b) The Date of Grant of an Option granted under Section 2.3 shall be the date of the annual meeting of stockholders of the Company to which the grant relates.

     (c) The Date of Grant of an Option granted under Section 2.4 shall be the date of the next annual meeting of stockholders after the election by the Eligible Director pursuant to the Compensation Plan to receive the Option in lieu of cash fees, except that, for an Eligible Director elected between annual stockholder meetings, the Date of Grant shall be the date of his or her election as a Director.

     Section 2.7. Vesting.

     (a) An Option granted under Section 2.2 shall be exercisable on or after the Date of Grant.

     (b) An Option granted under Section 2.3 shall become exercisable six months after the Date of Grant.

     (c) An Option granted under Section 2.4 shall become exercisable on the Payment Date(s) following the Date of Grant as provided in this Section 2.7(c). The number of Shares as to which an Option granted under Section 2.4 will become exercisable on each Payment Date after the Date of Grant shall equal the number of Shares subject to the Option divided by the number of Payment Dates occurring after the Date of Grant and before the first anniversary of the most recent annual meeting of stockholders of the Company.

     (d) Notwithstanding the other provisions of this Section 2.7, (i) an Option shall only become exercisable as provided in this Section 2.7 if the Optionee is a Director at the time the Option would otherwise become exercisable and (ii) upon the occurrence of a Change in Control, all Options outstanding at the time of the Change in Control shall become immediately exercisable.

     Section 2.8. Term of Options. The portion of an Option that is exercisable shall automatically and without notice terminate upon the earlier of (a) one (1) year after the Optionee ceases to be a Director for any reason or (b) ten (10) years after the Date of Grant of the Option. The portion of an Option that is not exercisable shall automatically and without notice terminate at the time the Optionee ceases to be a Director for any reason.

     Section 2.9. Exercise of Options. Any Option may be exercised in whole or in part to the extent exercisable in accordance with Section 2.7. An Option shall be deemed exercised when (i) the Company has received written notice of such exercise in accordance with the terms of the Option and (ii) full payment of the aggregate option price of the Shares as to which the Option is exercised has been made. Unless further limited by the Committee in any Option, the option price of any Shares purchased shall be paid solely in cash, by certified or cashier’s check, by money order, by personal check or with Shares owned by the Optionee for at least six months,

or by a combination of the foregoing. If the option price is paid in whole or in part with Shares, the value of the Shares surrendered shall be their Fair Market Value on the date received by the Company.

     Section 2.10. Adjustment of Shares.

     (a) If at any time while the Plan is in effect or unexercised Options are outstanding, there shall be any increase or decrease in the number of issued and outstanding Shares through the declaration of a stock dividend or through any recapitalization resulting in a stock split, combination or exchange of Shares, then and in such event:

     (i) appropriate adjustment shall be made in the maximum number of Shares then subject to being optioned under the Plan, and the numbers of Options to be granted under Sections 2.2, 2.3 and 2.4, so that the same proportion of the Company’s issued and outstanding Shares shall continue to be subject to being so optioned, and

     (ii) appropriate adjustment shall be made in the number of Shares and the exercise price per Share thereof then subject to any outstanding Option, so that the same proportion of the Company’s issued and outstanding Shares shall remain subject to purchase at the same aggregate exercise price.

     (b) In the event of a merger, consolidation or other reorganization of the Company in which the Company is not the surviving entity, the Board or the Committee may provide for any or all of the following alternatives: (i) for Options to become immediately exercisable, (ii) for exercisable Options to be cancelled immediately prior to such transaction, (iii) for the assumption by the surviving entity of the Plan and the Options, with appropriate adjustments in the number and kind of shares and exercise prices or (iv) for payment in cash or stock in lieu of and in complete satisfaction of Options.

     (c) Any fractional shares resulting from any adjustment under this Section 2.10 shall be disregarded and each Option shall cover only the number of full shares resulting from such adjustment.

     (d) Except as otherwise expressly provided herein, the issuance by the Company of shares of its capital stock of any class, or securities convertible into shares of capital stock of any class, either in connection with direct sale or upon the exercise of rights or warrants to subscribe therefor, or upon conversion of shares or obligations of the Company convertible into such shares or other securities, shall not affect, and no adjustment by reason thereof shall be made with respect to, the number of or exercise price of Shares then subject to outstanding Options granted under the Plan.

     (e) Without limiting the generality of the foregoing, the existence of outstanding Options granted under the Plan shall not affect in any manner the right or power of the Company to make, authorize or consummate (i) any or all adjustments, recapitalizations, reorganizations or other changes in the Company’s capital structure or its business; (ii) any merger or consolidation of the Company; (iii) any issue by the Company of debt securities, or preferred or preference stock that would rank above the Shares subject to outstanding Options; (iv) the dissolution or

liquidation of the Company; (v) any sale, transfer or assignment of all or any part of the assets or business of the Company; or (vi) any other corporate act or proceeding, whether of a similar character or otherwise.

     Section 2.11. Transferability of Options. Each Option shall provide that such Option shall not be transferable by the Optionee otherwise than by will or the laws of descent and distribution and that so long as an Optionee lives, only such Optionee or his guardian or legal representative shall have the right to exercise such Option.

     Section 2.12. Issuance of Shares. No person shall be, or have any of the rights or privileges of, a stockholder of the Company with respect to any of the Shares subject to any Option unless and until certificates representing such Shares (whether in physical or in book entry or other electronic form) shall have been issued and delivered to such person. As a condition of any transfer of the certificate for Shares, the Committee may obtain such agreements or undertakings, if any, as it may deem necessary or advisable to assure compliance with any provision of the Plan, any agreement or any law or regulation including, but not limited to, the following:

     (a) a representation, warranty or agreement by the Optionee to the Company, at the time any Option is exercised, that the Optionee is acquiring the Shares for investment and not with a view to, or for sale in connection with, the distribution of any such Shares; and

     (b) a representation, warranty or agreement to be bound by any legends that are, in the opinion of the Committee, necessary or appropriate to comply with the provisions of any securities law deemed by the Committee to be applicable to the issuance of the Shares and are endorsed upon the Share certificates.

ARTICLE III. RESTRICTED STOCK

     Section 3.1. Automatic Grants of Restricted Stock. Restricted Stock shall automatically be granted to Eligible Directors as provided in Sections 3.2 and 3.3. Each Restricted Stock grant shall be evidenced by an agreement containing such terms deemed necessary or desirable by the Committee that are not inconsistent with the Plan or any applicable law. No grant of Restricted Stock shall confer upon any person any right to continue to serve as a Director.

     Section 3.2. Automatic Annual Grants. Immediately after each annual meeting of stockholders of the Company, each Eligible Director shall automatically be granted ONE THOUSAND (1,000) shares of Restricted Stock.

     Section 3.3. Election to Receive Restricted Stock. If the Compensation Plan permits Eligible Directors to elect to receive Restricted Stock in lieu of all or part of Director fees otherwise payable in cash, each Eligible Director who has properly and timely made such election as provided in the Compensation Plan shall automatically be granted a number of Shares of Restricted Stock equal to (i) the amount of the fee such Eligible Director elects to receive in the form of Restricted Stock divided by (ii) the Fair Market Value of a Share on the Date of Grant multiplied by (iii) 1.2, with the result rounded to the nearest whole Share.

     Section 3.4. Date of Grant.

     (a) The Date of Grant of Restricted Stock granted under Section 3.2 shall be the date of the annual meeting of stockholders of the Company to which the grant relates.

     (b) The Date of Grant of Restricted Stock granted under Section 3.3 shall be the date of the next annual meeting of stockholders after the election by the Eligible Director pursuant to the Compensation Plan to receive the Restricted Stock in lieu of cash fees, except that, for an Eligible Director elected between annual stockholder meetings, the Date of Grant shall be the date of his or her election as a Director.

     Section 3.5. Vesting.

     (a) Restricted Stock granted under Section 3.2 shall vest six months after the Date of Grant.

     (b) Restricted Stock granted under Section 3.3 shall vest on the Payment Date(s) following the Date of Grant as provided in this Section 3.5(a). The number of Shares of Restricted Stock granted under Section 3.3 that will vest on each Payment Date after the Date of Grant shall equal the number of Shares of Restricted Stock granted divided by the number of Payment Dates occurring after the Date of Grant and before the first anniversary of the most recent annual meeting of stockholders of the Company.

     (c) Notwithstanding the other provisions of this Section 3.5, (i) Restricted Stock shall only vest as provided in this Section 3.5 if the holder is a Director at the time the Restricted Stock would otherwise vest and (ii) upon the occurrence of a Change in Control, all Restricted Stock issued under the Plan that is outstanding at the time of the Change in Control shall immediately vest.

     (d) Notwithstanding the vesting conditions set forth in the Plan or the Compensation Plan, the Committee may in its discretion at any time accelerate the vesting of Restricted Stock or otherwise waive or amend any conditions of a grant of Restricted Stock under the Plan.

     Section 3.6. Restrictions on Transfer. Stock certificates representing Restricted Stock granted to an Eligible Director under the Plan (whether in physical or in book entry or other electronic form) shall be registered in the Director’s name or, at the option of the Committee, not issued until such time as the Restricted Stock shall become vested or as otherwise determined by the Committee. If certificates are issued prior to the Shares of Restricted Stock becoming vested, either in physical or in book entry or other electronic form, such certificates shall either be held by the Company on behalf of the Director, or delivered to the Director bearing a legend to restrict transfer of the certificate until the Restricted Stock has vested, as determined by the Committee. The Director shall have the right to vote and receive dividends on the Restricted Stock before it has vested. Except as may otherwise be expressly permitted by the Committee, no Share of Restricted Stock may be sold, transferred, assigned or pledged by the Director until such Share has vested. In the event that a Director ceases to be a Director before all the Director’s Restricted Stock has vested, the Shares of Restricted Stock that have not vested shall be forfeited. At the time Restricted Stock vests (and, if the Director has been issued legended

certificates for Restricted Stock, upon the return of such certificates to the Company), a certificate for such vested Shares shall be delivered to the Director free of all restrictions.

     Section 3.7. Issuance of Shares. As a condition of the issuance of any certificate for Shares of Restricted Stock, the Committee may obtain such agreements or undertakings, if any, as it may deem necessary or advisable to assure compliance with any provision of the Plan, any agreement or any law or regulation including, but not limited to, the following:

     (a) a representation, warranty or agreement by the Eligible Director to the Company that the Eligible Director is acquiring the Shares for investment and not with a view to, or for sale in connection with, the distribution of any such Shares; and

     (b) a representation, warranty or agreement to be bound by any legends that are, in the opinion of the Committee, necessary or appropriate to comply with the provisions of any securities law deemed by the Committee to be applicable to the issuance of the Shares and are endorsed upon the Share certificates.

     Section 3.8. Section 83(b) Election. If a Director receives Restricted Stock that is subject to a “substantial risk of forfeiture,” the Director may elect under Section 83(b) of the Code to include in his or her gross income, for the taxable year in which the Restricted Stock is received, the Fair Market Value of such Restricted Stock on the Date of Grant. If the Director makes the Section 83(b) election, the Director shall (a) make such election in a manner that is satisfactory to the Committee, (b) provide the Company with a copy of such election and (c) agree to promptly notify the Company if any Internal Revenue Service or state tax agent, on audit or otherwise, questions the validity or correctness of such election or of the amount of income reportable on account of such election.

ARTICLE IV. ADDITIONAL PROVISIONS

     Section 4.1. Administration of the Plan. The Plan shall be administered by the Committee. The Committee shall have the authority to interpret the provisions of the Plan, to adopt such rules and regulations for carrying out the Plan as it may deem advisable, to decide conclusively all questions arising with respect to the Plan and to make all other determinations and take all other actions necessary or desirable for the administration of the Plan. All decisions and acts of the Committee shall be final and binding upon all affected Optionees and holders of Restricted Stock. If there is no Committee, the Board shall administer the Plan and in such case all references to the Committee shall be deemed to be references to the Board.

     Section 4.2. Adjustment of Shares. If at any time while the Plan is in effect, there shall be any increase or decrease in the number of issued and outstanding Shares through the declaration of a stock dividend or through any recapitalization resulting in a stock split, combination or exchange of Shares, the Committee shall make an appropriate adjustment in the number and kind of Shares then subject to being issued under the Plan, so that the same proportion of the Company’s issued and outstanding Shares shall continue to be subject to issuance under the Plan upon the exercise of Options or as Restricted Stock.

     Section 4.3. Amendment. The Board may amend or modify the Plan in any respect at any time, subject to stockholder approval if required by applicable law or regulation or by applicable stock exchange rules.

     Section 4.4. Duration and Termination. The Plan shall be of unlimited duration. The Board may suspend, discontinue or terminate the Plan at any time. Such action shall not impair any of the rights of any holder of any Option or Restricted Stock outstanding on the date of the Plan’s suspension, discontinuance or termination without the holder’s written consent.

     Section 4.5. Effective Date. The Plan amends and restates the Existing Plan in its entirety. Such amendment and restatement was adopted by the Board on March 3, 2005, to be effective April 26, 2005, with the Existing Plan remaining in effect until that date. The Board further amended the Plan on January 22, 2007 (with numbers of shares revised to reflect the 2-for-1 stock split on May 31, 2006).