Rubico registers offering of up to 50M shares

Rubico Inc. will begin quarterly earnings releases from the third quarter of 2026 while maintaining semi-annual SEC interim filings and audited annual reports.

Rhea-AI Filing Summary

Rubico Inc. (RUBI) filed a prospectus supplement covering the offering of up to 50,000,000 common shares, updating its existing Form F-1 registration statement. The supplement incorporates a Form 6-K that announces a transition from semi-annual to quarterly earnings reporting, starting with results for the third quarter and nine months ended September 30, 2026.

Each quarterly earnings release will include unaudited condensed financial statements and selected operating data but no accompanying notes. Rubico, a Marshall Islands–incorporated owner and operator of Suezmax and MR tankers and a megayacht newbuilding it intends to divest, will continue to furnish semi-annual interim statements and file audited annual financial statements on Form 20-F.

Key Figures

Common shares offered: Up to 50,000,000 common shares Quarterly reporting start period: Third quarter and nine months ended September 30, 2026 Suezmax tankers owned: 2 vessels, 157,000 dwt each +4 more

7 metrics

Common shares offered Up to 50,000,000 common shares Covered by the updated Form F-1 registration via this prospectus supplement

Quarterly reporting start period Third quarter and nine months ended September 30, 2026 First period for which Rubico plans to issue quarterly earnings releases

Suezmax tankers owned 2 vessels, 157,000 dwt each Modern, fuel-efficient, eco Suezmax tankers owned and operated by Rubico

MR tanker newbuildings owned 2 vessels, 47,499 dwt each Newbuildings scheduled for delivery in the third and fourth quarters of 2029

Additional MR tanker newbuilding via SPA 1 vessel, 47,499 dwt Owned by a shipowning company Rubico has agreed to acquire, delivery in second quarter 2029

Megayacht newbuilding length 60 meters Megayacht scheduled for delivery in the second quarter of 2027, which Rubico intends to divest

SPA closing deadline By September 30, 2026 Target closing date for the share purchase agreement to acquire the MR tanker-owning company

Key Terms

Prospectus Supplement, foreign private issuer, unaudited interim condensed consolidated financial statements, Form 20-F, +2 more

6 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.

foreign private issuer regulatory

"As a foreign private issuer, the Company will continue to furnish"

A foreign private issuer is a company organized outside the United States that meets tests showing it is primarily foreign-controlled and therefore qualifies for a different set of U.S. reporting rules. For investors, that means the company files less frequent or differently formatted disclosures with U.S. regulators and may follow home-country accounting and governance practices, so buying its stock is like dining at a well-reviewed restaurant that follows its home kitchen’s rules instead of the local menu — you get access but should check what standards apply.

unaudited interim condensed consolidated financial statements financial

"continue to furnish to the U.S. Securities and Exchange Commission unaudited interim condensed consolidated financial statements"

Form 20-F regulatory

"file audited annual consolidated financial statements with its annual report on Form 20-F"

Form 20-F is the standardized annual disclosure that non-U.S. companies must file with the U.S. securities regulator when their shares are traded in the U.S.; it contains audited financial statements, a plain-language description of the business, management discussion, governance details and key risk factors. It matters to investors because it provides a consistent, comparable company “report card” and rulebook, helping buyers assess financial health, governance and risks before investing.

Suezmax tankers technical

"owner and operator of two modern, fuel efficient, eco 157,000 dwt Suezmax tankers"

Suezmax tankers are a class of crude oil ships sized to be the largest vessels that can pass through the Suez Canal when fully loaded. Think of them like the biggest truck that can still fit under a low bridge—large enough to carry a lot of oil but constrained by a key route. Investors watch them because their availability and operating costs help set shipping capacity and freight rates, which influence oil prices, energy company margins, and shipping company cash flow.

share purchase agreement financial

"The Company has entered into a share purchase agreement to acquire a shipowning company"

A share purchase agreement is a written contract that outlines the terms and conditions for buying and selling shares of a company. It specifies details like the price, number of shares, and any special conditions, ensuring both buyer and seller agree on the transaction. For investors, it provides clarity and legal protection, making sure the purchase is clear and enforceable.

Offering Details

shelf

Offering

Offering Type shelf

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What does Rubico Inc. (RUBI) register in this prospectus supplement?

Rubico Inc. updates its Form F-1 registration to cover an offering of up to 50,000,000 common shares, incorporating new information from a Form 6-K, including its planned move to quarterly earnings reporting starting with third-quarter 2026 results.

How is Rubico Inc. (RUBI) changing its financial reporting schedule?

Rubico Inc. will transition from semi-annual to quarterly reporting of financial results, beginning with earnings for the third quarter and nine months ended September 30, 2026, which it expects to release during the fourth quarter of 2026.

What will be included in Rubico Inc.’s new quarterly earnings releases?

Each quarterly release will include unaudited condensed financial statements: a statement of operations for the quarter and year-to-date, a period-end balance sheet, and a summarized cash flow statement, plus selected operating data and updates; no notes to the financial statements will be included.

What SEC filings will Rubico Inc. (RUBI) continue to provide as a foreign private issuer?

As a foreign private issuer, Rubico Inc. will continue to furnish unaudited interim condensed consolidated financial statements with notes on a semi-annual basis and file audited annual consolidated financial statements with its annual report on Form 20-F.

What vessels and newbuildings does Rubico Inc. (RUBI) currently own or plan to acquire?

Rubico owns two 157,000 dwt Suezmax tankers, two 47,499 dwt MR tanker newbuildings scheduled for delivery in the third and fourth quarters of 2029, and a 60-meter megayacht newbuilding scheduled for delivery in the second quarter of 2027, which it intends to divest.

What pending acquisition has Rubico Inc. (RUBI) disclosed?

Rubico has entered a share purchase agreement to acquire a shipowning company that owns one 47,499 dwt MR tanker newbuilding scheduled for delivery in the second quarter of 2029, with closing of this share purchase agreement to occur by September 30, 2026.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 09/21/2026 - 04:16 PM Accepted by SEC EDGAR 09/21/2026 - 04:15 PM Learn about SEC filing dates

Filed Pursuant to Rule 424(b)(3)

Registration No. 333-295199

Registration No. 333-297277

PROSPECTUS SUPPLEMENT NO. 10

(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 September 21, 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 September 21, 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 September 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 [ X ]      Form 40-F [   ]

On September 21, 2026, the Registrant issued a press release, a copy of which is attached hereto as Exhibit 99.1 and is incorporated herein by reference.

Exhibit 99.1. Press release dated September 21, 2026.

The information contained in this Report is hereby incorporated by reference into the Registrant’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)
Date: September 21, 2026		/s/ Nikolaos Papastratis
		Nikolaos Papastratis
		Chief Financial Officer

EXHIBIT 99.1

Rubico Announces Transition to Quarterly Reporting of Financial Results

ATHENS, Greece, Sept. 21, 2026 (GLOBE NEWSWIRE) -- Rubico Inc. (Nasdaq: RUBI) (the “Company” or “Rubico”), a global provider of shipping transportation services specializing in the ownership of vessels, announced today that it will transition from semi-annual to quarterly reporting of its financial results, beginning with the announcement of its results for the third quarter and nine months ended September 30, 2026, which the Company expects to release during the fourth quarter of 2026.

Each quarterly earnings release will include unaudited condensed financial statements, comprising a statement of operations for the relevant quarterly and year-to-date periods, a balance sheet as of the end of the relevant period and a summarized statement of cash flows for the relevant quarterly and year-to-date periods, together with selected operating data and operational updates. The quarterly earnings releases will not include accompanying notes to the financial statements. As a foreign private issuer, the Company will continue to furnish to the U.S. Securities and Exchange Commission unaudited interim condensed consolidated financial statements with accompanying notes on a semi-annual basis, and to file audited annual consolidated financial statements with its annual report on Form 20-F.

The transition to quarterly earnings reporting reflects the Company’s commitment to enhanced transparency and more frequent communication with the investment community, and aligns the frequency of the Company’s reporting with that of many of its listed peers.

About the Company

Rubico Inc. is a global provider of shipping transportation services specializing in the ownership of vessels. The Company is an international owner and operator of two modern, fuel efficient, eco 157,000 dwt Suezmax tankers. Furthermore, the Company owns two 47,499 dwt MR tanker newbuildings scheduled for delivery in the third and fourth quarters of 2029 and a 60-meter newbuilding megayacht scheduled for delivery in the second quarter of 2027, which the Company intends to divest. In addition, the Company has entered into a share purchase agreement to acquire a shipowning company that owns one high-specification 47,499 dwt MR tanker newbuilding scheduled for delivery in the second quarter of 2029, with closing of this share purchase agreement to occur by September 30, 2026.

The Company is incorporated under the laws of the Republic of the Marshall Islands and has executive offices in Athens, Greece. The Company’s common shares trade on the Nasdaq Capital Market under the symbol “RUBI”.

Please visit the Company’s website at: https://rubicoinc.com/

For further information please contact:

Nikolaos Papastratis
Chief Financial Officer
Rubico Inc.
Tel: +30 210 812 8107
Email: npapastratis@rubicoinc.com

Forward-Looking Statements

Matters discussed in this press release may constitute forward-looking statements. The Private Securities Litigation Reform Act of 1995 provides safe harbor protections for forward-looking statements in order to encourage companies to provide prospective information about their business. Forward-looking statements include statements concerning plans, objectives, goals, strategies, future events or performance, and underlying assumptions and other statements, which are other than statements of historical facts, including statements regarding the timing, frequency and content of the Company’s future financial reporting and earnings releases.

The Company desires to take advantage of the safe harbor provisions of the Private Securities Litigation Reform Act of 1995 and is including this cautionary statement in connection with this safe harbor legislation. The words “believe,” “anticipate,” “intends,” “estimate,” “forecast,” “project,” “plan,” “potential,” “may,” “should,” “expect,” “pending” and similar expressions identify forward-looking statements. The forward-looking statements in this press release are based upon various assumptions, many of which are based, in turn, upon further assumptions, including without limitation, our management’s examination of historical operating trends, data contained in our records and other data available from third parties. Although we believe that these assumptions were reasonable when made, because these assumptions are inherently subject to significant uncertainties and contingencies which are difficult or impossible to predict and are beyond our control, we cannot assure you that we will achieve or accomplish these expectations, beliefs or projections. Please see the Company’s filings with the Securities and Exchange Commission for a more complete discussion of these and other risks and uncertainties. The information set forth herein speaks only as of the date hereof, and the Company disclaims any intention or obligation to update any forward-looking statements as a result of developments occurring after the date of this communication.