Exhibit 8.1

October 19, 2026

Re: Rubico Inc.

To Whom It May Concern:

We have acted as counsel to Rubico Inc., a Marshall Islands corporation (the “Company”), in connection with the issuance and sale by the Company of (i) Senior Convertible Notes (the “Notes”) in an aggregate initial principal amount of up to $15,000,000, (ii) common shares, par value $0.01 per share, issuable from time to time upon conversion of the Notes (the “Note Shares”), (iii) common share purchase warrants (the “Warrants”) to purchase common shares with an aggregate initial cash exercise price of up to $15,000,000, (iv) common shares issuable from time to time upon exercise of the Warrants (the “Warrant Shares”), (v) common shares issuable at each closing of a sale of Notes and Warrants pursuant to the Purchase Agreement (the “Commitment Shares”) and/or pre-funded warrants issuable at each closing of a sale of Notes and Warrants pursuant to the Purchase Agreement (the “Pre-Funded Warrants”) and (vi) common shares issuable from time to time upon exercise of the Pre-Funded Warrants (the “Pre-Funded Warrant Shares” and, together with the Notes, Note Shares, Warrants, Warrant Shares, and Pre-Funded Warrants the “Securities”). The Securities are being issued and sold pursuant to the Company’s Registration Statement on Form F-3 (333-297207) declared effective by the U.S. Securities and Exchange Commission pursuant to the provisions of the Securities Act of 1933, as amended (the “Securities Act”) on July 14, 2026 (the “Registration Statement”), the prospectus dated July 14, 2026, as thereafter amended or supplemented (the “Base Prospectus”), and the prospectus supplement to the Base Prospectus dated October 16, 2026 (the “Prospectus Supplement”).

As such counsel, we have examined originals or copies (certified or otherwise identified to our satisfaction) of the following documents:

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In such examination, we have assumed (a) the legal competence or capacity of persons or entities (other than the Company) to complete the execution of documents, (b) the genuineness of all signatures and the authenticity of all documents submitted to us as originals, (c) the conformity to original documents of all documents submitted to us as conformed or photostatic copies, (d) that the documents reviewed by us in connection with the rendering of the opinions set forth herein are true, correct and complete, and (e) the truthfulness of each statement as to all factual matters contained in any document or certificate encompassed within the due diligence review undertaken by us. As to matters of fact material to this opinion that have not been independently established, we have relied upon the representations and certificates of officers or representatives of the Company and of public officials, in each case as we have deemed relevant and appropriate. We have not independently verified the facts so relied on.

We have reviewed the discussion set forth under the caption “Material U.S. Federal Income and Marshall Islands Tax Considerations of the Securities” in the Prospectus Supplement. Based on the representations, covenants, assumptions, conditions and qualifications described in such section, and taking into account the fact that the discussions set forth in such section do not purport to discuss all possible U.S. federal income tax consequences of the ownership and disposition of the Securities, and subject to the qualifications, limitations and assumptions set forth herein, we confirm that the discussions set forth in such section, to the extent they constitute summaries of law or legal conclusions, unless otherwise noted, constitute our opinion with respect to the material U.S. federal income tax consequences of the ownership and disposition of the Securities, as of the date of the Registration Statement, and accurately state our views as to the tax matters discussed therein (except for the representations and statements of fact of the Company included under such caption, as to which we express no opinion). We express no opinion as to any U.S. federal income tax consequences other than the opinion set forth above.

We have reviewed the discussion set forth in the set forth under the caption “Material U.S. Federal Income and Marshall Islands Tax Considerations of the Securities—Marshall Islands Tax Consequences” in the Prospectus Supplement. Based on the facts as set forth in the Registration Statement and the Prospectus Supplement, and having regard to legal considerations which we deem relevant, and subject to the qualifications, limitations and assumptions set forth herein, we confirm that the statements in such discussion, to the extent they constitute legal conclusions, unless otherwise noted, are the opinion of Watson Farley & Williams LLP with respect to Marshall Islands tax consequences as of the date of the Prospectus Supplement (except for the representations and statements of fact of the Company included under such caption, as to which we express no opinion).

Our opinions and the tax discussion as set forth in the Registration Statement, Base Prospectus, and Prospectus Supplement are, as applicable, based on the current provisions of the Internal Revenue Code of 1986, as amended, the Treasury Regulations promulgated thereunder, published pronouncements of the Internal Revenue Service which may be cited or used as precedents and case law, and the law of the Republic of the Marshall Islands as in effect on the date hereof, any of which may be changed at any time with retroactive effect. This opinion is expressed as of the date hereof, and we are under no obligation to supplement or revise our opinion to reflect any legal developments or factual matters arising subsequent to the date hereof or the impact of any information, document, certificate, record, statement, representation, covenant, or assumption relied upon herein that becomes incorrect or untrue.

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We consent to the filing of this opinion as an exhibit to a Current Report on Form 6-K, the discussion of this opinion in the Registration Statement and to the references to our firm in the Registration Statement and the Prospectus. In giving this consent, we do not hereby admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act, or the rules and regulations promulgated thereunder, nor do we admit that we are experts with respect to any part of the Registration Statement within the meaning of the term “expert” as used in the Securities Act.

Very truly yours,

/s/ Watson Farley & Williams LLP

Watson Farley & Williams LLP