8-K

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or Section 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): March 3, 2026

Quartzsea Acquisition Corporation

(Exact name of registrant as specified in its charter)

Registrant’s telephone number, including area code: (212) 612-1400

Not Applicable

(Former name or former address, if changed since last report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation to the registrant under any of the following provisions:

Securities registered pursuant to Section 12(b) of the Act:

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).

Emerging growth company ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 1.01 Entry into a Material DefinitiveAgreement.

On March 3, 2026, Quartzsea Acquisition Corporation (the “Company”) entered into Amendment No. 1 to the Underwriting Agreement (the “Amendment”) with Polaris Advisory Partners, LLC (f/k/a SPAC Advisory Partners), a division of Kingswood Capital Partners LLC, as representative of the several underwriters (the “Representative”), and Kingswood Capital Partners LLC.

The Amendment amends that certain Underwriting Agreement, dated March 17, 2025, by and between the Company, the Representative, and Kingswood Capital Partners LLC, to revise the calculation and payment terms of the deferred underwriting commission.

Pursuant to the Amendment, the Deferred Underwriting Commission will be payable from the trust account upon consummation of the Company’s initial business combination and equals 4.00% of the gross proceeds from the sale of the firm units and option units, subject to a cap equal to 4.00% of the funds remaining in the trust account after giving effect to all properly submitted redemptions in connection with the initial business combination. The Amendment also clarifies that the underwriters may waive the Deferred Underwriting Commission prior to the consummation of the Company’s initial business combination.

The foregoing description of the Amendment is qualified in its entirety by reference to the full text of the Amendment, which is filed as Exhibit 10.1 hereto and incorporated herein by reference.

Item 9.01. Financial Statements and Exhibits.

1

SIGNATURE

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 hereunto duly authorized.

2

Exhibit 10.1

AMENDMENT NO. 1 TO UNDERWRITING AGREEMENT

QUARTZSEA ACQUISITION CORPORATION

This Amendment No. 1 to the Underwriting Agreement (this “Amendment”) is entered into as of March 3, 2026, by and between Quartzsea Acquisition Corporation, a Cayman Islands exempted company (the “Company”), Polaris Advisory Partners, LLC (f/k/a and SPAC Advisory Partners), a division of Kingswood Capital Partners LLC, as representative of the several underwriters named therein (the “Representative”), and Kingswood Capital Partners LLC (“Kingswood”).

RECITALS

WHEREAS, the Company, the Representative, and Kingswood are parties to that certain Underwriting Agreement, dated March 17, 2025 (the “Underwriting Agreement”);

WHEREAS, the parties desire to amend the Underwriting Agreement to revise the calculation and payment terms of the Deferred Underwriting Commission; and

WHEREAS, capitalized terms used but not defined herein have the meanings set forth in the Underwriting Agreement.

NOW, THEREFORE, in consideration of the mutual covenants set forth herein and for other good and valuable consideration, the receipt and sufficiency of which are hereby acknowledged, the parties agree as follows:

Section 1.3 of the Underwriting Agreement is hereby deleted in its entirety and replaced with the following:

1.3 Deferred Underwriting Commission. The Underwriters agree that 4.00% of the gross proceeds from the sale of the Firm Units ($2,880,000) and the Option Units (up to $432,000), if any (collectively, the “Deferred Underwriting Commission”), will be deposited and held in the Trust Account and payable directly from the Trust Account, without accrued interest, to the Underwriters for their own accounts upon consummation of the Company’s initial Business Combination. The Underwriters acknowledge and agree that the Deferred Underwriting Commission shall be payable only to the extent of, and shall in no event exceed, an amount equal to 4.00% of the funds remaining in the Trust Account after giving effect to all properly submitted redemptions in connection with the initial Business Combination. Each Underwriter, severally and not jointly, reserves the right in its sole discretion to waive the Deferred Underwriting Commission at any time prior to the initial Business Combination by providing written notice to the Company. In the event that the Company is unable to consummate a Business Combination and CST, as the trustee of the Trust Account (in this context, the “Trustee”), commences liquidation of the Trust Account as provided in the Trust Agreement, the Underwriters agree that: (i) they shall forfeit any rights or claims to the Deferred Underwriting Commission; and (ii) the Deferred Underwriting Commission, together with all other amounts on deposit in the Trust Account, shall be distributed on a pro-rata basis among the Public Shareholders.

Except as expressly amended hereby, the Underwriting Agreement remains unmodified and in full force and effect.

This Amendment shall be governed by and construed in accordance with the laws of the State of New York, without giving effect to its conflicts of law principles.

This Amendment may be executed in counterparts (including by electronic or PDF signature), each of which shall be deemed an original, and all of which together shall constitute one and the same instrument.

[Signature Page Follows]

IN WITNESS WHEREOF, the parties have executed this Amendment as of the date first above written.