UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 8-A

FOR REGISTRATION OF CERTAIN CLASSES OF SECURITIES

PURSUANT TO SECTION 12(b) OR (g) OF THE

SECURITIES EXCHANGE ACT OF 1934

Blue Water Acquisition Corp. IV

(Exact name of registrant as specified in its charter)

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

If this form relates to the registration of a class of securities pursuant to Section 12(b) of the Exchange Act and is effective pursuant to General Instruction A.(c) or (e), check the following box. ☒

If this form relates to the registration of a class of securities pursuant to Section 12(g) of the Exchange Act and is effective pursuant to General Instruction A.(d) or (e), check the following box. ☐

If this form relates to the registration of a class of securities concurrently with a Regulation A offering, check the following box. ☐

Securities Act registration statement or Regulation A offering statement file number to which this form relates: 333-291959

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

N/A

(Title of class)

(Title of class)

INFORMATION REQUIRED IN REGISTRATION STATEMENT

Item 1. Description of Registrant’s Securities to be Registered.

The securities to be registered hereby are (1) units, each consisting of one Class A ordinary share and one-half of one redeemable warrant, (2) Class A ordinary shares, par value $0.0001 per share, and (3) warrants entitling the holder thereof to purchase one Class A ordinary share at a price of $11.50 per share of Blue Water Acquisition Corp. IV, a Cayman Islands exempted company (the “Registrant”). The description of the units, Class A ordinary shares and warrants set forth under the heading “Description of Securities” in the Registrant’s prospectus forming a part of its Registration Statement on Form S-1 (File No. 333-291959), originally filed with the Securities and Exchange Commission on December 5, 2025, as thereafter amended and supplemented from time to time (the “Registration Statement”), to which this Form 8-A relates is incorporated by reference herein. Any form of prospectus or prospectus supplement to the Registration Statement that includes such descriptions and that is subsequently filed is hereby also incorporated by reference herein.

Item 2. Exhibits.

Pursuant to the Instructions as to Exhibits for Form 8-A, no exhibits are required to be filed, because no other securities of the Registrant are registered on The New York Stock Exchange and the securities registered hereby are not being registered pursuant to Section 12(g) of the Securities Exchange Act of 1934, as amended.

SIGNATURE

Pursuant to the requirements of Section 12 of the Securities Exchange Act of 1934, the registrant has duly caused this registration statement to be signed on its behalf by the undersigned, thereto duly authorized.