Rubico Inc美股招股说明书(2025-12-30版)

PROSPECTUS SUPPLEMENT NO. 8(TO PROSPECTUS DATED SEPTEMBER 19, 2025) Up to 15,000,000 Common Shares RUBICO INC. This is a supplement (the “Prospectus Supplement”) to the prospectus, dated September 19, 2025 (as supplemented or amendedfrom time to time, the “Prospectus”) of Rubico Inc. (the “Company”), which forms a part of the Company’s Registration Statement on This Prospectus Supplement is being filed to update and supplement the information included in the Prospectus with theinformation contained in the Company’s Report on Form 6-K, furnished to the U.S. Securities and Exchange Commission (the This Prospectus Supplement should be read in conjunction with, and delivered with, the Prospectus and is qualified by referenceto the Prospectus except to the extent that the information in this Prospectus Supplement supersedes the information contained in the This Prospectus Supplement is not complete without, and may not be delivered or utilized except in connection with, theProspectus, including any amendments or supplements to it. Investing in our securities involves a high degree of risk. See “Risk Factors” beginning on page 12 of the Prospectus for adiscussion of information that should be considered in connection with an investment in our securities. Neither the Commission nor any state securities commission has approved or disapproved of these securities ordetermined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense. The date of this prospectus supplement is December 29, 2025. INFORMATION CONTAINED IN THIS FORM 6-K REPORT Attached to this report on Form 6-K asExhibit 99.1are the proxy materials for the 2026 Annual Meeting of Shareholders of Rubico Inc.(the “Corporation”). Attached to this report on Form 6-K asExhibit 99.2is the proxy card for the 2026 Annual Meeting of Shareholders of the Corporation. SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on itsbehalf by the undersigned, thereunto duly authorized. RUBICO INC.(Registrant)By:/s/ Kalliopi OrnithopoulouName:Kalliopi OrnithopoulouTitle:Chief Executive Officer Date: December 29, 2025 December 29, 2025 TO THE SHAREHOLDERS OF RUBICO INC. Enclosed is a Notice of the 2026 Annual Meeting of Shareholders (the “Meeting”) of Rubico Inc. (the “Corporation”), whichwill be held at the offices of the Corporation, 20 Iouliou Kaisara Str, 19002, Paiania, Athens, Greece, on January 15, 2026 at 12:00 p.m. At this Meeting, shareholders of the Corporation will consider and vote upon the following proposals: 1.To elect two Class A Directors to serve until the 2029 Annual Meeting of Shareholders (“Proposal One”); 2.To ratify the appointment of Deloitte Certified Public Accountants S.A., as the Corporation’s independent auditors for thefiscal year ending December 31, 2026 (“Proposal Two”); 3.To approve one or more amendments to the Corporation’s Amended and Restated Articles of Incorporation to effect one ormore reverse stock splits of the shares of the Corporation’s common stock issued and outstanding at the time of the reversesplit at a cumulative exchange ratio of between one-for-two and one-for-250, inclusive, with the Corporation’s board ofdirectors (including any duly constituted committee thereof, the “Board”) to determine, in its sole discretion, whether toimplement any reverse stock split, as well as the specific timing and ratio, within such approved range of ratios, and to 4.To transact such other business as may properly come before the meeting or any adjournment thereof. Only holders of record of shares of our common stock, par value $0.01 per share, (the “Common Shares”) and shares of ourSeries D Preferred Stock, par value $0.01 per share, (the “Series D Preferred Shares” and, together with the Common Shares, the“Shares”) at the close of business on December 5, 2025 will be entitled to vote at the Meeting. Each shareholder of record on that date isentitled to one (1) vote for each Common Share, one thousand (1,000) votes for each Series D Preferred Share then held. The holders of Adoption of Proposal One requires the affirmative vote of a plurality of the votes cast by shareholders entitled to vote and votingat the Meeting. Adoption of Proposal Two requires the affirmative vote of a majority of the votes cast by shareholders entitled to vote and Consenting to electronic delivery of future proxy materials.You can help us save significant printing and mailing expenses byconsenting to access proxy materials, including the notice of the meeting, proxy statement and annual report electronically via e-mail orthe internet. You can choose this option by following the instructions atwww.proxyvote.com. If you choose to receive your proxymaterials and annual report electronically, then prior to next year’s shareholders’ meeting you will receive notification when the proxy You are cordially invited to attend