<PAGE>

EXHIBIT 12.1

                                 CERTIFICATIONS

I, John A. Jacobson, President and Chief Executive Officer of Offshore Systems
International Ltd., certify that:

1. I have reviewed this annual report on Form 20-F of Offshore Systems
International Ltd.;

2. Based on my knowledge, this annual report does not contain any untrue
statement of a material fact or omit to state a material fact necessary to make
the statements made, in light of the circumstances under which such statements
were made, not misleading with respect to the period covered by this annual
report;

3. Based on my knowledge, the financial statements, and other financial
information included in this annual report, fairly present in all material
respects the financial condition, results of operations and cash flows of the
Company as of, and for, the periods presented in this annual report;

4. The Company's other certifying officers and I are responsible for
establishing and maintaining disclosure controls and procedures (as defined in
Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial
reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the
Company and have:

      a) Designed such disclosure controls and procedures, or caused such
      disclosure controls and procedures to be designed under our supervision,
      to ensure that material information relating to the company, including its
      consolidated subsidiaries, is made known to us by others within those
      entities, particularly during the period in which this report is being
      prepared;

      b) Designed such internal control over financial reporting, or caused such
      internal control over financial reporting to be designed under our
      supervision, to provide reasonable assurance regarding the reliability of
      financial reporting and the preparation of financial statements for
      external purposes in accordance with generally accepted accounting
      principles;

      c) Evaluated the effectiveness of the company's disclosure controls and
      procedures and presented in this report our conclusions about the
      effectiveness of the disclosure controls and procedures, as of the end of
      the period covered by this report based on such evaluation; and

      d) Disclosed in this report any change in the company's internal control
      over financial reporting that occurred during the period covered by the
      annual report that has materially affected, or is reasonably likely to
      materially affect, the company's internal control over financial
      reporting; and

5. The Company's other certifying officers and I have disclosed, based on our
most recent evaluation of internal control over financial reporting, to the
Company's auditors and the audit committee of the Company's board of directors
(or persons performing the equivalent functions):

      a) all significant deficiencies and material weaknesses in the design or
      operation of internal controls over financial reporting which are
      reasonably likely to adversely affect the Company's ability to record,
      process, summarize and report financial information; and

      b) any fraud, whether or not material, that involves management or other
      employees who have a significant role in the Company's internal control
      over financial reporting; and

Date: May 30, 2005

                                        /s/ "John A. Jacobson"
                                        ------------------------------------
                                                  John A. Jacobson
                                        President and Chief Executive Officer

<PAGE>

EXHIBIT 12.1

                                 CERTIFICATIONS

I, John T. Sentjens, Corporate Controller of Offshore Systems International
Ltd., certify that:

1. I have reviewed this annual report on Form 20-F of Offshore Systems
International Ltd.;

2. Based on my knowledge, this annual report does not contain any untrue
statement of a material fact or omit to state a material fact necessary to make
the statements made, in light of the circumstances under which such statements
were made, not misleading with respect to the period covered by this annual
report;

3. Based on my knowledge, the financial statements, and other financial
information included in this annual report, fairly present in all material
respects the financial condition, results of operations and cash flows of the
Company as of, and for, the periods presented in this annual report;

4. The Company's other certifying officers and I are responsible for
establishing and maintaining disclosure controls and procedures (as defined in
Exchange Act Rules 13a-15(e) and 15d-15(e)) and internal control over financial
reporting (as defined in Exchange Act Rules 13a-15(f) and 15d-15(f)) for the
Company and have:

      a) Designed such disclosure controls and procedures, or caused such
      disclosure controls and procedures to be designed under our supervision,
      to ensure that material information relating to the company, including its
      consolidated subsidiaries, is made known to us by others within those
      entities, particularly during the period in which this report is being
      prepared;

      b) Designed such internal control over financial reporting, or caused such
      internal control over financial reporting to be designed under our
      supervision, to provide reasonable assurance regarding the reliability of
      financial reporting and the preparation of financial statements for
      external purposes in accordance with generally accepted accounting
      principles;

      c) Evaluated the effectiveness of the company's disclosure controls and
      procedures and presented in this report our conclusions about the
      effectiveness of the disclosure controls and procedures, as of the end of
      the period covered by this report based on such evaluation; and

      d) Disclosed in this report any change in the company's internal control
      over financial reporting that occurred during the period covered by the
      annual report that has materially affected, or is reasonably likely to
      materially affect, the company's internal control over financial
      reporting; and

5. The Company's other certifying officers and I have disclosed, based on our
most recent evaluation of internal control over financial reporting, to the
Company's auditors and the audit committee of the Company's board of directors
(or persons performing the equivalent functions):

      a) all significant deficiencies and material weaknesses in the design or
      operation of internal controls over financial reporting which are
      reasonably likely to adversely affect the Company's ability to record,
      process, summarize and report financial information; and

      b) any fraud, whether or not material, that involves management or other
      employees who have a significant role in the Company's internal control
      over financial reporting; and

Date: May 30, 2005

                                         /s/ "John T. Sentjens"
                                         --------------------------------
                                                    John T. Sentjens
                                                  Corporate Controller