Rubico Inc美股招股说明书(2025-11-07版)

Up to 15,000,000 Common Shares RUBICO INC. This is a supplement (“Prospectus Supplement”) to the prospectus, dated September 19, 2025 (“Prospectus”) of Rubico Inc.(the “Company”), which forms a part of the Company’s Registration Statement on Form F-1 (Registration No. 333-288796). On November 6, 2025, the Company filed a Current Report on Form 6-K with the U.S. Securities and Exchange Commission(the “Commission”) as set forth below. 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 Securities and Exchange Commission nor any state securities commission has approved or disapproved ofthese securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminaloffense. The date of this prospectus supplement is November 6, 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 November 2025 Commission File Number: 001-42684 RUBICO INC.(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 Public Offering On November 6, 2025, Rubico Inc. (“we” or the “Company”), closed a firm commitment underwritten public offering (the “Offering”)of 12,315,270 units (“Units”), each Unit consisting of one share of our common stock, par value $0.01 per share (“Common Shares”)and one Class A Warrant (each, a “Warrant”) to purchase one Common Share, at a public offering price of $0.609 per Unit. The Company has also granted Maxim Group LLC, the representative of the underwriters in the Offering (the “Representative”), a 45-day option to purchase up to an additional 1,847,290 additional Common Shares at the offering price and/or up to 1,847,290 Warrants,to cover over-allotments, if any. On November 6, 2025, the Representative partially exercised its over-allotment option with respect to1,847,290 Warrants. In addition, we agreed to issue to the Representative warrants to purchase a number of Common Shares equal to 5.0% of the totalnumber of Common Shares sold in the Offering, including any Common Shares sold pursuant to the over-allotment option granted tothe Representative (the “Representative Warrants”). Representative Warrants to purchase 615,763 Common Shares were issued inconnection with the closing of the Offering. The Representative Warrants have substantially similar terms as the Warrants issued in theOffering. The Offering was made pursuant to a registration statement on Form F-1, as amended (File No. 333-290426), filed with the Securitiesand Exchange Commission (the “Commission”), which became effective with the Commission on November 4, 2025. The aggregate gross proceeds to the Company from the Offering, before deducting underwriting discounts and other expenses payableby the Company, were approximately $7.5 million. On November 5, 2025, the Company released a press release furnished herewith as Exhibit 99.1, announcing the pricing of theOffering. Description of the Warrants The following summary of certain terms and provisions of the Warrants is not complete and is subject to, and qualified in its entiretyby, the provisions of the form of Warrant furnished as an exhibit to this report. Exercisability. The Warrants are immediately exercisable at any time after their issuance and at any time up to the date that is one(1) year after their issuance. The Warrants will be exercisable, at the option of each holder, in whole or in part by delivering to us aduly executed exercise notice with payment in full in immediately available funds for the number of Common Shares purchased uponsuch exercise (except in the case of a cashless exercise or zero cash exercise, as discussed below). We may be required to pay certainamounts as liquidated damages as specified in the warrants in the event we do not deliver Common Shares upon exercise of thewarrants within the time periods specified in the warrants. No fractional Common Shares will be issued in connection with theexercise of a warrant. Cashless Exercise and Zero Cash Exe