Rubico Inc. (RUBI) adds 15M-share prospectus update and wide reverse split range

Rhea-AI Filing Summary

Rubico Inc. filed a prospectus supplement linked to its Form F-1 registration, covering an offering of up to 15,000,000 common shares. The supplement adds information from a recent Report of Foreign Private Issuer describing shareholder approval of amendments to the Amended and Restated Articles of Incorporation permitting one or more reverse stock splits at a cumulative exchange ratio between one-for-two and one-for-250. The board of directors may, in its sole discretion, decide whether to implement a reverse split, select the specific ratio within this range, and file the corresponding amendment on or before January 15, 2027.

Insights

Capital markets analyst

Rubico aligns its share structure flexibility with an existing 15,000,000-share offering.

Rubico Inc. maintains an offering capacity of up to 15,000,000 common shares under its Form F-1, while updating disclosure to reflect shareholder approval for a potential reverse stock split. The approved cumulative exchange ratio spans from one-for-two to one-for-250%, giving the board wide latitude on how aggressively to consolidate shares.

The board may choose if and when to implement any reverse split, and at what specific ratio within the range, provided action occurs by January 15, 2027. This structure can help manage share price and listing standards, but the economic impact on existing holders will depend on the chosen ratio and whether the full share offering capacity is ultimately used.

Key Figures

Registered share capacity: 15,000,000 common shares Reverse split exchange ratio range: one-for-two to one-for-250 Reverse split implementation deadline: January 15, 2027 +1 more

4 metrics

Registered share capacity 15,000,000 common shares Maximum number of Rubico Inc. common shares covered by the prospectus

Reverse split exchange ratio range one-for-two to one-for-250 Cumulative exchange ratio range approved by shareholders for potential reverse stock splits

Reverse split implementation deadline January 15, 2027 Latest date by which any reverse stock split must be implemented

Form F-3 file number 333-297207 Registration statement into which the Form 6-K information is incorporated by reference

Key Terms

Prospectus Supplement, reverse stock splits, cumulative exchange ratio, Report of Foreign Private Issuer, +1 more

5 terms

Prospectus Supplement regulatory

"This is a supplement (the “Prospectus Supplement”) to the prospectus"

A prospectus supplement is an additional document provided alongside a company's main offering details, offering updated or extra information about a specific financial product being sold. It helps investors understand the latest terms, risks, and details of the investment, similar to how an update or revision clarifies or expands on original instructions, ensuring they have current and complete information before making a decision.

reverse stock splits financial

"to effect one or more reverse stock splits of the shares of the Company’s common stock"

A reverse stock split is when a company combines multiple existing shares into fewer higher-priced shares—like trading four small slices of a pie for one larger slice. It doesn’t change the overall value of an investor’s holdings immediately, but it raises the per-share price and can matter to investors because it can affect market perception, stock exchange listing eligibility, and trading liquidity, and it changes share counts used in investor metrics.

cumulative exchange ratio financial

"at a cumulative exchange ratio of between one-for-two and one-for-250, inclusive"

Report of Foreign Private Issuer regulatory

"FORM 6-K REPORT OF FOREIGN PRIVATE ISSUER"

A report of a foreign private issuer is a formal filing that a non‑U.S. company makes to U.S. regulators to share important business, financial, or governance information with American investors. Think of it as a regular update or press packet that keeps investors informed about events that could change a company’s value—like earnings, management changes, contracts, or regulatory developments—so investors can make timely, informed decisions.

Form F-3 regulatory

"incorporated by reference into the Company’s registration statement on Form F-3"

Form F-3 is a U.S. securities filing that lets eligible foreign companies pre-register and then quickly sell shares or other securities to raise money, because they already meet ongoing reporting and size tests. For investors it signals that the company is up-to-date with regulatory disclosure and has an efficient way to issue new securities — similar to a pre-approved credit line — which can mean faster capital raises but also potential dilution of existing holdings.

Offering Details

shelf

Offering

Offering Type shelf

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Available on EDGAR 07/10/2026 - 04:12 PM Accepted by SEC EDGAR 07/10/2026 - 04:11 PM Learn about SEC filing dates

FAQ

What share amount is covered by Rubico Inc. (RUBI) in this prospectus supplement?

The prospectus supplement relates to an existing offering of up to 15,000,000 common shares of Rubico Inc. It updates that prospectus by incorporating information from a recent Form 6-K filing.

What reverse stock split range did Rubico Inc. (RUBI) shareholders approve?

Shareholders approved amendments allowing one or more reverse stock splits at a cumulative exchange ratio between one-for-two and one-for-250. The board can select the specific ratio within this range.

By when must any approved reverse stock split for Rubico Inc. (RUBI) be implemented?

Any reverse stock split or splits must be implemented on or before January 15, 2027. The board may file the necessary amendment with the Marshall Islands registrar by that date.

Who decides whether Rubico Inc. (RUBI) will actually execute a reverse stock split?

Rubico’s board of directors has sole discretion to determine whether to implement any reverse stock split, including the specific timing and ratio, within the shareholder-approved range.

Which SEC registration statements are affected by this Rubico Inc. (RUBI) supplement and Form 6-K?

The supplement relates to Rubico’s Form F-1 registration (multiple file numbers) and incorporates the Form 6-K by reference into its Form F-3 registration statement No. 333-297207.

Filed Pursuant to Rule 424(b)(3)

Registration No. 333-288796

Registration No. 333-291884

Registration No. 333-293441

Registration No. 333-294944

Registration No. 333-297276

PROSPECTUS SUPPLEMENT NO. 18

(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 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. 333-288796, 333-291884, 333-293441, 333-294944 and 333-297276), 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 12 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.

	RUBICO INC.
	(Registrant)
	By:	/s/ Nikolaos Papastratis
	Name:	Nikolaos Papastratis
	Title:	Chief Financial Officer

Date: July 10, 2026