<PAGE>

                                                                   EXHIBIT 10.17

                               SEVERANCE AGREEMENT

      AGREEMENT between SEABULK INTERNATIONAL, INC., a Delaware corporation (the
"Company"), and Hubert E. Thyssen ("Executive"),

                              W I T N E S S E T H :

      WHEREAS, the Company desires to attract and retain certain key employees
and, accordingly, the Compensation Committee of the Board of Directors of the
Company (the "Board") has approved the Company entering into a severance
agreement with Executive in order to encourage his continued service to the
Company; and

      WHEREAS, Executive is prepared to commit such services in return for
specific arrangements with respect to severance compensation and other benefits;

      NOW, THEREFORE, in consideration of the foregoing and for other good and
valuable consideration, the Company and Executive agree as follows:

      1. DEFINITIONS.

            (a) "Annual Compensation" shall mean an amount equal to the greater
of:

                  (i) Executive's annual base salary at the annual rate in
effect at the date of his Involuntary Termination plus the amount of his Annual
Bonus, as defined below;

                  (ii) Executive's annual base salary at the annual rate in
effect sixty days prior to the date of his Involuntary Termination plus the
amount of his Annual Bonus, as defined below; or

                 (iii) Executive's annual base salary at the annual rate in
effect immediately prior to a Change of Control if Executive's employment shall
be subject to an Involuntary Termination within two years after such Change of
Control.

Plus the amount of his Annual Bonus, as defined below.

The term `Annual Bonus' shall mean the annual bonus most recently paid by the
Company to Executive prior to the date of his Involuntary Termination; provided,
however, that if Executive has not received an annual bonus from the Company at
any time prior to the date of his Involuntary Termination, then the `Annual
Bonus' shall equal the amount of Executive's target annual bonus for the year in
which such termination occurs.

            (b) "Change in Duties" shall mean:

                  (i) The occurrence, within two years after the date upon which
a Change of Control occurs, of any one or more of the following:

<PAGE>

                        (1) A significant change in the nature or scope of
Executive's authorities or duties from those applicable to him immediately prior
to the date on which a Change of Control occurs;

                        (2) A reduction in Executive's base salary from that
provided to him immediately prior to the date on which a Change of Control
occurs;

                        (3) A diminution in Executive's eligibility to
participate in bonus, stock option, incentive award and other compensation plans
which provide opportunities to receive compensation which are the greater of (A)
the opportunities provided by the Company (including its subsidiaries) for
executives with comparable duties or (B) the opportunities under any such plans
under which he was participating immediately prior to the date on which a Change
of Control occurs;

            (c) "Change in Control" shall be deemed to have occurred if (i) a
tender offer shall be made and consummated for the ownership of 50% or more of
the outstanding voting securities of the Company eligible to vote in the
election of directors generally, (ii) the Company shall be merged or
consolidated with another entity, or substantially all of the assets of the
Company shall be sold or transferred to another entity if, in any such case, as
a result of such merger, consolidation or sale, less than 50% of the outstanding
voting securities of the resulting entity eligible to vote in the election of
directors generally (or comparable governing body) shall be owned in the
aggregate by the former shareholders of the Company, (iii) a person, including a
"group" (other than a trustee or other fiduciary holding securities under an
employee benefit plan of the Company or any member of the Existing Group),
within the meaning of Section 3(a)(9) or of Section 13(d)(3) (as in effect on
the date hereof) of the Securities Exchange Act of 1934, shall acquire 50% or
more of the outstanding voting securities of the Company eligible to vote in the
election of directors generally (whether directly, indirectly, beneficially or
of record), or (iv) the Company is to be dissolved or liquidated. For purposes
hereof, ownership of voting securities shall take into account and shall include
ownership as determined by applying the provisions of Rule 13d-3(d)(1)(i) (as in
effect on the date hereof) pursuant to the Securities Exchange Act of 1934. For
the purpose of this definition, a "member of the Existing Group" means any
person or entity controlled by, or under common control with, any of Credit
Suisse First Boston Private Equity, Carlyle Group or Riverstone Holdings, LLC.

            (d) "Compensation Committee" shall mean the Compensation Committee
of the Board.

            (e) "Disability" shall mean that, as a result of Executive's
incapacity due to physical or mental illness, he shall have been absent from the
full-time performance of his duties for six-consecutive months and he shall not
have returned to full-time performance of his duties within thirty days after
written notice of termination is given to Executive by the Company (provided,
however, that such notice may not be given prior to thirty days before the
expiration of such six-month period).

                                       2
<PAGE>

            (f) "Involuntary Termination" shall mean any termination of
Executive's employment with the Company which:

                  (i) does not result from a resignation by Executive (other
than a resignation pursuant to clause (ii) of this subparagraph (f)); or

                  (ii) results from a resignation by Executive within two years
after the date upon which a Change of Control occurs and is on or before the
date which is sixty days after the date upon which Executive receives notice of
a Change in Duties;

provided, however, the term "Involuntary Termination" shall not include a
Termination for Cause or any termination as a result of death, Disability, or
Retirement.

            (g) "Monthly Severance Amount" shall mean an amount equal to
one-twelfth of Executive's Annual Compensation.

            (h) "Retirement" shall mean Executive's resignation on or after the
date he reaches age sixty-five.

            (i) "Severance Amount" shall mean an amount equal to the Executive's
Annual Compensation.

            (j) "Severance Period" shall mean:

            (i) in the case of an Involuntary Termination, a period commencing
on the date of such Involuntary Termination and continuing for twelve (12)
months.

            (k) "Termination for Cause" shall mean termination of Executive's
employment by the Company (or its subsidiaries) by reason of Executive's (i)
gross negligence in the performance of his duties, (ii) willful and continued
failure to perform his duties, (iii) willful engagement in conduct which is
materially injurious to the Company or its subsidiaries (monetarily or
otherwise) or (iv) conviction of a felony or a misdemeanor involving moral
turpitude.

      2. SERVICES. Executive agrees that he will render services to the Company
(as well as any subsidiary thereof or successor thereto) during the period of
his employment to the best of his ability and in a prudent and businesslike
manner and that he will devote substantially the same time, efforts and
dedication to his duties as heretofore devoted.

      3. TERMINATION OTHER THAN WITHIN TWO YEARS AFTER A CHANGE OF CONTROL.
Subject to the provisions of Paragraph 7(i) hereof, if Executive's employment by
the Company or any subsidiary thereof or successor thereto shall be subject to
an Involuntary Termination which occurs prior to a Change of Control or after
the date which is two years after a Change of Control occurs, then the Company
will, as additional compensation for services rendered to the Company (including
its subsidiaries), pay to Executive the following amounts (subject to any
applicable payroll or other taxes required to be withheld and any employee
benefit premiums) and take the following actions after the last day of
Executive's employment with the Company:

                                       3
<PAGE>

            (a) Pay Executive the Monthly Severance Amount on the first day of
each month throughout the Severance Period.

            (b) Cause Executive and those of his dependents (including his
spouse) who were covered under the Company's medical and dental benefit plans on
the day prior to Executive's Involuntary Termination to continue to be covered
under such plans throughout the Severance Period, without any cost to Executive;
provided, however, that (i) such coverage shall terminate if and to the extent
Executive becomes eligible to receive medical and dental coverage from a
subsequent employer (and any such eligibility shall be promptly reported to the
Company by Executive) and (ii) if Executive (and/or his spouse) would have been
entitled to retiree medical and/or dental coverage under the Company's plans had
he voluntarily retired on the date of such Involuntary Termination, then such
retiree coverages shall be continued as provided under such plans.

      4. TERMINATION WITHIN TWO YEARS AFTER A CHANGE OF CONTROL. If Executive's
employment by the Company or any subsidiary thereof or successor thereto shall
be subject to an Involuntary Termination which occurs within two years after the
date upon which a Change of Control occurs, then the Company will, as additional
compensation for services rendered to the Company (including its subsidiaries),
pay to Executive the following amounts (subject to any applicable payroll or
other taxes required to be withheld and any employee benefit premiums) and take
the following actions after the last day of Executive's employment with the
Company:

            (a) Pay Executive a lump sum cash payment in an amount equal to the
Severance Amount on or before the fifth day after the last day of Executive's
employment with the Company.

            (b) Cause Executive and those of his dependents (including his
spouse) who were covered under the Company's medical and dental benefit plans on
the day prior to Executive's Involuntary Termination to continue to be covered
under such plans throughout the Severance Period, without any cost to Executive;
provided, however, that (i) such coverage shall terminate if and to the extent
Executive becomes eligible to receive medical and dental coverage from a
subsequent employer (and any such eligibility shall be promptly reported to the
Company by Executive) and (ii) if Executive (and/or his spouse) would have been
entitled to retiree medical and/or dental coverage under the Company's plans had
he voluntarily retired on the date of such Involuntary Termination, then such
retiree coverages shall be continued as provided under such plans.

            (c) Cause any and all outstanding options to purchase common stock
of the Company and any and all restricted stock which have not become
nonforfeitable held by Executive to become immediately exercisable and
nonforfeitable in full; and cause Executive's accrued benefits under any and all
nonqualified deferred compensation plans sponsored by the Company to become
immediately nonforfeitable.

            (d) Cause any and all outstanding options to purchase common stock
of the Company held by Executive to remain exercisable for twelve months after
the last day of Executive's employment with the Company (but in no event shall
any such option be exercisable

                                       4
<PAGE>

for (i) a longer period than the original term of such option or (ii) a shorter
period than that already provided for under the terms of such option).

      5. INTEREST ON LATE PAYMENTS. If any payment provided for in Paragraph
3(a) or Paragraph 4(a) hereof is not made when due, the Company shall pay to
Executive interest on the amount payable from the date that such payment should
have been made under such paragraph until such payment is made, which interest
shall be calculated at 10%.

      6. CERTAIN ADDITIONAL PAYMENTS BY THE COMPANY.

            (a) Notwithstanding anything to the contrary in this Agreement, in
the event that any payment or distribution by the Company to or for the benefit
of Executive, whether paid or payable or distributed or distributable pursuant
to the terms of this Agreement or otherwise (a "Payment"), would be subject to
the excise tax imposed by Section 4999 of the Internal Revenue Code of 1986, as
amended, or any interest or penalties with respect to such excise tax (such
excise tax, together with any such interest or penalties, are hereinafter
collectively referred to as the "Excise Tax"), the Company shall pay to
Executive an additional payment (a "Gross-up Payment") in an amount such that
after payment by Executive of all taxes (including any interest or penalties
imposed with respect to such taxes), including any Excise Tax imposed on any
Gross-up Payment, Executive retains an amount of the Gross-up Payment equal to
the Excise Tax imposed upon the Payments. The Company and Executive shall make
an initial determination as to whether a Gross-up Payment is required and the
amount of any such Gross-up Payment. Executive shall notify the Company
immediately in writing of any claim by the Internal Revenue Service which, if
successful, would require the Company to make a Gross-up Payment (or a Gross-up
Payment in excess of that, if any, initially determined by the Company and
Executive) within ten days of the receipt of such claim. The Company shall
notify Executive in writing at least five days prior to the due date of any
response required with respect to such claim if it plans to contest the claim.
If the Company decides to contest such claim, Executive shall cooperate fully
with the Company in such action; provided, however, the Company shall bear and
pay directly or indirectly all costs and expenses (including additional interest
and penalties) incurred in connection with such action and shall indemnify and
hold Executive harmless, on an after-tax basis, for any Excise Tax or income
tax, including interest and penalties with respect thereto, imposed as a result
of the Company's action. If, as a result of the Company's action with respect to
a claim, Executive receives a refund of any amount paid by the Company with
respect to such claim, Executive shall promptly pay such refund to the Company.
If the Company fails to timely notify Executive whether it will contest such
claim or the Company determines not to contest such claim, then the Company
shall immediately pay to Executive the portion of such claim, if any, which it
has not previously paid to Executive.

      7. GENERAL.

            (a) TERM. The effective date of this Agreement is April 3, 2003.
Within sixty (60) days after February 3, 2005, and within sixty (60) days after
each successive 24-month period of time thereafter that this Agreement is in
effect, the Company shall have the right to review this Agreement, and in its
sole discretion either continue and extend this Agreement, terminate this
Agreement, and/or offer Executive a different agreement. The Compensation
Committee will vote on whether to so extend, terminate, and/or offer Executive a
different

                                       5
<PAGE>

agreement and will notify Executive of such action within said sixty-day time
period mentioned above. This Agreement shall remain in effect until so
terminated and/or modified by the Company. Failure of the Compensation Committee
to take any action within said sixty days shall be considered as an extension of
this Agreement for an additional 24-month period of time. Notwithstanding
anything to the contrary contained in this "sunset provision," it is agreed that
if a Change of Control occurs while this Agreement is in effect, then this
Agreement shall not be subject to termination or modification under this "sunset
provision," and shall remain in force for a period of 24 months after such
Change of Control, and if within said 24 months the contingency factors occur
which would entitle Executive to the benefits as provided herein, this Agreement
shall remain in effect in accordance with its terms. If, within such 24 months
after a Change of Control, the contingency factors that would entitle Executive
to said benefits do not occur, thereupon this 24-month "sunset provision" shall
again be applicable with the sixty-day time period for Compensation Committee
action to thereafter commence at the expiration of said 24 months after such
Change of Control and on each 24-month anniversary date thereafter.

            (b) INDEMNIFICATION. If Executive shall obtain any money judgment or
otherwise prevail with respect to any litigation brought by Executive or the
Company to enforce or interpret any provision contained herein, the Company, to
the fullest extent permitted by applicable law, hereby indemnifies Executive for
his reasonable attorneys' fees and disbursements incurred in such litigation and
hereby agrees (i) to pay in full all such fees and disbursements and (ii) to pay
prejudgment interest on any money judgment obtained by Executive from the
earliest date that payment to him should have been made under this Agreement
until such judgment shall have been paid in full, which interest shall be
calculated at 10% plus the prime or base rate of interest announced by CITIGROUP
(or any successor thereto) at its principal office in New York, and shall change
when and as any such change in such prime or base rate shall be announced by
such bank.

            (c) PAYMENT OBLIGATIONS ABSOLUTE. The Company's obligation to pay
(or cause one of its subsidiaries to pay) Executive the amounts and to make the
arrangements provided herein shall be absolute and unconditional and shall not
be affected by any circumstances, including, without limitation, any set-off,
counterclaim, recoupment, defense or other right which the Company (including
its subsidiaries) may have against him or anyone else. All amounts payable by
the Company (including its subsidiaries hereunder) shall be paid without notice
or demand. Executive shall not be obligated to seek other employment in
mitigation of the amounts payable or arrangements made under any provision of
this Agreement, and, except as provided in Paragraphs 3(b) and 4(b) hereof, the
obtaining of any such other employment shall in no event effect any reduction of
the Company's obligations to make (or cause to be made) the payments and
arrangements required to be made under this Agreement.

            (d) SUCCESSORS. This Agreement shall be binding upon and inure to
the benefit of the Company and any successor of the Company, by merger or
otherwise. This Agreement shall also be binding upon and inure to the benefit of
Executive and his estate. If Executive shall die prior to full payment of
amounts due pursuant to this Agreement, such amounts shall be payable pursuant
to the terms of this Agreement to his estate.

            (e) SEVERABILITY. Any provision in this Agreement which is
prohibited or unenforceable in any jurisdiction by reason of applicable law
shall, as to such jurisdiction, be

                                       6
<PAGE>

ineffective only to the extent of such prohibition or unenforceability without
invalidating or affecting the remaining provisions hereof, and any such
prohibition or unenforceability in any jurisdiction shall not invalidate or
render unenforceable such provision in any other jurisdiction.

            (f) NON-ALIENATION. Executive shall not have any right to pledge,
hypothecate, anticipate or assign this Agreement or the rights hereunder, except
by will or the laws of descent and distribution.

            (g) NOTICES. Any notices or other communications provided for in
this Agreement shall be sufficient if in writing. In the case of Executive, such
notices or communications shall be effectively delivered if hand delivered to
Executive at his principal place of employment or if sent by registered or
certified mail to Executive at the last address he has filed with the Company.
In the case of the Company, such notices or communications shall be effectively
delivered if sent by registered or certified mail to the Company at its
principal executive offices.

            (h) CONTROLLING LAW. This Agreement shall be governed by, and
construed in accordance with, the laws of the State of Florida.

            (i) RELEASE. As a condition to the receipt of any benefit under
Paragraph 3 or Paragraph 4 hereof, Executive shall first execute a release, in
the form established by the Company, releasing the Company, its shareholders,
partners, officers, directors, employees and agents from any and all claims and
from any and all causes of action of any kind or character, including but not
limited to all claims or causes of action arising out of Executive's employment
with the Company or the termination of such employment.

            (j) FULL SETTLEMENT. If Executive is entitled to and receives the
benefits provided hereunder, performance of the obligations of the Company
hereunder will constitute full settlement of all claims that Executive might
otherwise assert against the Company on account of his termination of
employment.

            (k) UNFUNDED OBLIGATION. The obligation to pay amounts under this
Agreement is an unfunded obligation of the Company (including its subsidiaries),
and no such obligation shall create a trust or be deemed to be secured by any
pledge or encumbrance on any property of the Company (including its
subsidiaries).

            (l) NOT A CONTRACT OF EMPLOYMENT. This Agreement shall not be deemed
to constitute a contract of employment, nor shall any provision hereof affect
(a) the right of the Company (or its subsidiaries) to discharge Executive at
will or (b) the terms and conditions of any other agreement between the Company
or its affiliates and Executive except however that the provisions in this
Severance Agreement shall supercede any and all provisions in such other
agreement as they may relate to termination of employment and severance.

            (m) NUMBER AND GENDER. Wherever appropriate herein, words used in
the singular shall include the plural and the plural shall include the singular.
The masculine gender where appearing herein shall be deemed to include the
feminine gender.

                                       7
<PAGE>

      IN WITNESS WHEREOF, the parties hereto have executed this Agreement on the
21st day of April, 2003.

                                                     "EXECUTIVE"

                                                     /s/ Hubert E. Thyssen
                                                     ---------------------------
                                                     Hubert E. Thyssen

                                                     "COMPANY"

                                                     SEABULK INTERNATIONAL, INC.

                                                     By:/s/ Gerhard E. Kurz
                                                        ------------------------
                                                        Gerhard E. Kurz
                                                        Chief Executive Officer

                                       8