Adage (BWIV) reports 8.38% holding — 1,125,000 Class A shares

Rhea-AI Filing Summary

Adage Capital Management and affiliated principals report beneficial ownership of 1,125,000 Class A ordinary shares (8.38%) of Blue Water Acquisition Corp. IV.

The percentage is calculated using 13,425,000 Class A Ordinary Shares outstanding as of March 23, 2026, cited from Exhibit 99.1 to the company Form 8-K. The filing discloses shared voting and dispositive power and is signed by the reporting persons on May 13, 2026.

Key Figures

Reported shares beneficially owned: 1,125,000 shares Percent of class: 8.38% Shares outstanding (context): 13,425,000 shares +2 more

5 metrics

Reported shares beneficially owned 1,125,000 shares Class A ordinary shares held by Adage and principals

Percent of class 8.38% Calculated using 13,425,000 shares outstanding as of <date>March 23, 2026</date>

Shares outstanding (context) 13,425,000 shares Outstanding Class A Ordinary Shares as of <date>March 23, 2026</date> (per Exhibit 99.1)

Cover-page shared voting power 1,125,000 shares Shared voting power reported on cover page

CUSIP (units) G1368A120 CUSIP for units that include the Class A Ordinary Shares

Key Terms

Schedule 13G, Beneficially owned, Shared dispositive power, Class A ordinary shares

4 terms

Schedule 13G regulatory

"Item 1. | (a) | Name of issuer: Blue Water Acquisition Corp."

A Schedule 13G is a formal document that investors file with the government when they acquire a large ownership stake in a company, usually for investment purposes rather than control. It helps keep the public informed about who owns significant parts of a company's shares, which can influence how the company is managed and how investors make decisions. Filing this schedule is important for transparency and understanding the ownership landscape of publicly traded companies.

Beneficially owned financial

"Item 4. | (a) | Amount beneficially owned: The information required by Item 4(a)"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

Shared dispositive power regulatory

"Row 8 | Shared Dispositive Power 1,125,000.00"

Class A ordinary shares financial

"Title of class of securities: Class A ordinary shares, par value $0.0001 per share"

Class A ordinary shares are a type of ownership stake in a company that typically grants voting rights to shareholders, allowing them to have a say in important company decisions. They often come with priority in receiving dividends or profits, making them attractive to investors seeking influence and potential income. These shares help distinguish different levels of ownership and rights within a company's stock structure.

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Accepted by SEC EDGAR 05/13/2026 - 09:09 AM Learn about SEC filing dates

FAQ

What stake does Adage report in Blue Water Acquisition Corp. IV (BWIV)?

Adage reports beneficial ownership of 1,125,000 Class A ordinary shares, representing 8.38% of the class. The percent is calculated using 13,425,000 shares outstanding as of March 23, 2026, per Exhibit 99.1 to the company Form 8-K.

Who are the reporting persons on the Schedule 13G for BWIV?

The statement is filed by Adage Capital Management, L.P. and two individuals: Robert Atchinson and Phillip Gross, each identified with shared voting and dispositive power over the reported 1,125,000 shares.

How was the 8.38% ownership percentage calculated in the filing?

The filing calculates 8.38% using an aggregate of 13,425,000 Class A Ordinary Shares outstanding as of March 23, 2026, a figure cited from Exhibit 99.1 to the company’s Form 8-K filed March 27, 2026.

Does the Schedule 13G show sole voting or dispositive power for Adage?

The cover data shows 0 sole voting power and 1,125,000 shared voting power, and similarly 0 sole dispositive power with 1,125,000 shared dispositive power over the reported shares.

What identifying information about the shares is included in the filing?

The filing lists the class as Class A ordinary shares, par value $0.0001 and provides the units' CUSIP G1368A120. It notes the Class A Ordinary Shares themselves have no separate CUSIP.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

Blue Water Acquisition Corp. IV

(Name of Issuer)

Class A ordinary shares, par value $0.0001 per share

(Title of Class of Securities)

G1368A120

(CUSIP Number)

03/31/2026

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): G1368A120

1

Names of Reporting Persons

Adage Capital Management, L.P.

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,125,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,125,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,125,000.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

8.38 %

12

Type of Reporting Person (See Instructions)

IA, PN

SCHEDULE 13G

CUSIP Number(s): G1368A120

1

Names of Reporting Persons

Robert Atchinson

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,125,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,125,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,125,000.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

8.38 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

CUSIP Number(s): G1368A120

1

Names of Reporting Persons

Phillip Gross

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 1,125,000.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 1,125,000.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

1,125,000.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

8.38 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Blue Water Acquisition Corp. IV
(b)	Address of issuer's principal executive offices: 15 E. Putnam Avenue, Suite 363, Greenwich, Connecticut 06830
Item 2.
(a)	Name of person filing: This statement is filed by: (i) Adage Capital Management, L.P., a Delaware limited partnership ("ACM"), as the investment manager of Adage Capital Partners, L.P., a Delaware limited partnership ("ACP"), with respect to the Class A ordinary shares, par value $0.0001 per share ("Class A Ordinary Shares") of Blue Water Acquisition Corp. IV, a Cayman Islands exempted company (the "Company") directly held by ACP; (ii) Robert Atchinson ("Mr. Atchinson"), as (1) managing member of Adage Capital Advisors, L.L.C., a limited liability company organized under the laws of the State of Delaware ("ACA"), managing member of Adage Capital Partners GP, L.L.C., a limited liability company organized under the laws of the State of Delaware ("ACPGP"), general partner of ACP, and (2) managing member of Adage Capital Partners, L.L.C., a Delaware limited liability company ("ACPLLC"), general partner of ACM, with respect to the Class A Ordinary Shares directly held by ACP; and (iii) Phillip Gross ("Mr. Gross"), as (1) managing member of ACA, managing member of ACPGP, and (2) managing member of ACPLLC, general partner of ACM, with respect to the Class A Ordinary Shares directly held by ACP. The foregoing persons are hereinafter sometimes collectively referred to as the "Reporting Persons." Any disclosures herein with respect to persons other than the Reporting Persons are made on information and belief after making inquiry to the appropriate party. The filing of this statement should not be construed in and of itself as an admission by any Reporting Person as to beneficial ownership of the securities reported herein. The Class A Ordinary Shares have no CUSIP number. The CUSIP number for the units which include the Class A Ordinary Shares is G1368A120.
(b)	Address or principal business office or, if none, residence: The address of the business office of each of the Reporting Persons is 200 Clarendon Street, 52nd Floor, Boston, Massachusetts 02116.
(c)	Citizenship: ACM is a limited partnership organized under the laws of the State of Delaware. Messrs. Gross and Atchinson are citizens of the United States.
(d)	Title of class of securities: Class A ordinary shares, par value $0.0001 per share
(e)	CUSIP Number(s): G1368A120
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: The information required by Item 4(a) is set forth in Row 9 of the cover page for each of the Reporting Persons and is incorporated herein by reference. The percentage set forth in this Schedule 13G is calculated based upon an aggregate of 13,425,000 Class A Ordinary Shares outstanding as of March 23, 2026, as reported in Exhibit 99.1 to the Company's Current Report on Form 8-K filed with the Securities and Exchange Commission on March 27, 2026.
(b)	Percent of class: 8.38%
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: The information required by Item 4(c)(i) is set forth in Row 5 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
	(ii) Shared power to vote or to direct the vote: The information required by Item 4(c)(ii) is set forth in Row 6 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
	(iii) Sole power to dispose or to direct the disposition of: The information required by Item 4(c)(iii) is set forth in Row 7 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
	(iv) Shared power to dispose or to direct the disposition of: The information required by Item 4(c)(iv) is set forth in Row 8 of the cover page for each of the Reporting Persons and is incorporated herein by reference.
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. See Item 2(a).
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

Adage Capital Management, L.P.

Signature:	/s/ Robert Atchinson
Name/Title:	By: Adage Capital Partners, L.L.C., its General Partner, By: Robert Atchinson, its Managing Member
Date:	05/13/2026

Robert Atchinson

Signature:	/s/ Robert Atchinson
Name/Title:	Robert Atchinson, individually
Date:	05/13/2026

Phillip Gross

Signature:	/s/ Phillip Gross
Name/Title:	Phillip Gross, individually
Date:	05/13/2026

Exhibit Information

Exhibit 99.1: Joint Filing Agreement