Filed Pursuant to Rule 424(b)(3)
Registration No. 333-295199
Registration No. 333-297277
PROSPECTUS SUPPLEMENT NO. 3
(TO PROSPECTUS DATED MAY 1, 2026)
Up to 50,000,000 Common Shares
RUBICO INC.
This is a supplement (the “Prospectus Supplement”)
to the prospectus, dated May 1, 2026 (as supplemented or amended from time to time, the “Prospectus”) of Rubico Inc. (the
“Company”), which forms a part of the Company’s Registration Statement on Form F-1 (Registration Nos. 333-295199 and
333-297277), as amended from time to time.
This Prospectus Supplement is being filed to update
and supplement the information included in the Prospectus with the information contained in the Company’s Report on Form 6-K, furnished
to the U.S. Securities and Exchange Commission (the “Commission”) on July 10, 2026 (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 by reference to the Prospectus except to the extent that the information in
this Prospectus Supplement supersedes the information contained in the Prospectus.
This Prospectus Supplement is not complete without,
and may not be delivered or utilized except in connection with, the Prospectus, including any amendments or supplements to it.
Investing in our securities involves a high degree
of risk. See “Risk Factors” beginning on page 10 of the Prospectus for 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 or determined if this prospectus is truthful or complete. Any representation
to the contrary is a criminal offense.
The date of this prospectus supplement is July 10, 2026.
UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
FORM 6-K
REPORT OF FOREIGN PRIVATE ISSUER PURSUANT TO RULE 13a-16 OR
15d-16 UNDER THE SECURITIES EXCHANGE ACT OF 1934
For the month of July 2026
Commission File Number: 001-42684
RUBICO INC.
(Translation of registrant’s name into English)
20 Iouliou Kaisara Str
19002, Paiania
Athens – 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 ☐
On July 9, 2026, Rubico Inc. (the “Company”)
held a Special Meeting of Shareholders (the “Special Meeting”). At the Special Meeting, the shareholders of the Company approved
and adopted a proposal to approve one or more amendments to the Company’s Amended and Restated Articles of Incorporation to effect
one or more reverse stock splits of the shares of the Company’s common stock issued and outstanding at the time of the reverse split
at a cumulative exchange ratio of between one-for-two and one-for-250, inclusive, with the Company’s board of directors (including
any duly constituted committee thereof, the “Board”) to determine, in its sole discretion, whether to implement any reverse
stock split, as well as the specific timing and ratio, within such approved range of ratios, and to authorize the Board to implement any
such reverse stock split by filing any such amendment with the Registrar of Corporations of the Republic of the Marshall Islands; provided
that any such reverse stock split or splits are implemented on or before January 15, 2027.
The information contained in this Report is hereby incorporated by reference into the Company’s registration statement on Form F-3
(File No. 333-297207).
SIGNATURES
Pursuant to the requirements of the Securities Exchange
Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned, thereunto duly authorized.
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RUBICO INC. |
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(Registrant) |
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By: |
/s/ Nikolaos Papastratis |
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Name: |
Nikolaos Papastratis |
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Title: |
Chief Financial Officer |
Date: July 10, 2026