Rubico Inc美股招股说明书(2025-12-08版)

12,315,270 Units,Each Unit Consisting of One Common Share or One Pre-funded Warrant to Purchase One Common Shareand One Class A Warrant to Purchase One Common Share 615,763 Representative Warrants (and up to 12,315,270 Common Shares Underlying the Pre-funded Warrants, up to 49,261,080 Common Shares Underlying theClass A Warrants and up to 2,463,052 Common Shares Underlying the Representative Warrants) RUBICO INC. This is a supplement (the “Prospectus Supplement”) to the prospectus, dated November 4, 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 onForm F-1 (Registration No. 333-290426), as amended from time to time. 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“Commission”) on December 4, 2025 (the “Form 6-K”). Accordingly, the Form 6-K is attached to this Prospectus Supplement. This Prospectus Supplement should be read in conjunction with, and delivered with, the Prospectus and is qualified byreference to the Prospectus except to the extent that the information in this Prospectus Supplement supersedes the informationcontained in the Prospectus. 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 Prospectusfor a discussion 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 8, 2025. UNITED STATES SECURITIES AND EXCHANGE COMMISSIONWashington, D.C. 20549 FORM 6-K REPORT OF FOREIGN PRIVATE ISSUER PURSUANT TO RULE 13A-16 OR 15D-16 UNDER THE SECURITIESEXCHANGE ACT OF 1934 For the month of December 2025 Commission File Number: 001-42684 (Translation of registrant’s name into English) 20 Iouliou Kaisara Str19002 PaianiaAthens, Greece(Address of principal executive office) Indicate by check mark whether the registrant files or will file annual reports under cover of Form 20-F or Form 40-F: Form 20-F☒Form 40-F☐ INFORMATION CONTAINED IN THIS FORM 6-K REPORT On December 4, 2025, the Registrant issued a press release, a copy of which is attached hereto asExhibit 99.1. SIGNATURES Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the registrant has duly caused this report to besigned on its behalf by the undersigned hereunto duly authorized. Rubico Inc. By:/s/ Nikolaos PapastratisNikolaos PapastratisChief Financial Officer Date: December 8, 2025 Rubico Inc. Announces Letter of Intent for Acquisition of Newbuilding Mega Yacht ATHENS, GREECE, Dec. 4, 2025 (GLOBE NEWSWIRE) – Rubico Inc.(Nasdaq: RUBI) (the “Company” or “Rubico”), a globalprovider of shipping transportation services specializing in the ownership of vessels, announced today it has entered into a letter ofintent (the “LOI”) for the potential acquisition from Top Ships Inc. of a newbuilding mega yacht, the M/Y Sanlorenzo 1150Exp, withexpected delivery in the second quarter of 2027, or the Newbuilding Yacht. The Newbuilding Yacht has a length of 60 meters and agross tonnage of 1,150 tons with 6 guest cabins and is able to accommodate 12 guests and 15 crew. The Company will make an advance cash payment of $4.0 million that will be credited against the acquisition price of theNewbuilding Yacht or refunded to the extent the Company does not elect to purchase the Newbuilding Yacht. The exclusivity periodunder the LOI will expire on March 31st, 2026. Up to that date the Company will conduct a due diligence process and evaluation ofthe potential transaction taking into account market conditions and other factors, and there can be no assurance that potentialtransaction will be consummated. A special independent committee composed of independent members of the Company's board ofdirectors will negotiate and approve any potential acquisition pursuant to the LOI. About the Company Rubico Inc. is a global provider of shipping transportation services specializing in the ownership of vessels. The Company is aninternational owner and operator of two modern, fuel efficient, eco 157,000 dwt Suezmax tankers. The Company is incorporated under the laws of the Republic of the Marshall Islands and has executive offices in Athens, Greece. TheCompany's common shares trade on the Nasdaq Capital Market under the symbol “RUBI”.Please visit the Company’s website at:https://rubicoinc.com/ For