[SCHEDULE 13D/A] Transocean Ltd. SEC Filing

Rhea-AI Filing Summary

Amendment No. 8 to Schedule 13D reports that Frederik W. Mohn, Perestroika AS and Perestroika (Cyprus) Ltd. (together, the Reporting Persons) beneficially own 95,074,894 to 95,418,301 shares of Transocean Ltd. (Shares), representing approximately 10.1% of the outstanding class based on 943,124,986 shares outstanding as of July 29, 2025. The filing describes a change in the form of ownership when Perestroika Sub exchanged $213,367,000 principal amount of 2.5% Senior Guaranteed Exchangeable Bonds into Shares on April 21, 2023, and discloses multiple cash purchases by Perestroika Sub between February 2024 and September 2025, including 4,000,000 shares bought at $3.05 per share in the Issuer’s registered offering on September 26, 2025. Mr. Mohn directly holds 22,148 shares plus vested RSU-related rights and has sole voting/dispositive power over 343,407 shares and shared voting/dispositive power over 95,074,894 shares. The filing replaces prior Item 1 text and states all other Items remain unchanged from the earlier Schedule 13D filings.

Positive

• Material disclosure of a ~10.1% beneficial stake in Transocean Ltd., improving transparency of major shareholder positions.
• Conversion of $213,367,000 principal of exchangeable bonds into equity was disclosed, clarifying change in ownership form.
• Detailed transaction history including multiple cash purchases and a 4,000,000-share purchase at $3.05 per share on September 26, 2025.

Negative

• Shared voting power concentration (95,074,894 shares) may concentrate influence among related Reporting Persons.
• Filing does not state intentions regarding future plans or corporate actions, leaving investor implications unspecified.

Insights

Securities Analyst

TL;DR: Reporting Persons hold an approximately 10.1% stake after exchanges and purchases, a material disclosed ownership position in Transocean Ltd.

The Schedule 13D/A documents a material beneficial ownership position of ~10.1% of outstanding Transocean shares by Perestroika-related parties and Mr. Mohn. The filing clarifies a conversion of $213.4 million principal of exchangeable bonds into equity and enumerates multiple open-market and registered-offering purchases, including a 4.0 million-share purchase at $3.05 per share on September 26, 2025. Voting and dispositive powers are split between sole holdings of Mr. Mohn (343,407 shares) and shared control of 95,074,894 shares held through Perestroika entities. This is a clear, reportable change in the form and composition of ownership that investors should note when assessing shareholder composition.

Corporate Governance Expert

TL;DR: The amendment documents a concentrated block held with shared voting power, raising governance significance for Transocean's shareholder base.

The disclosure shows that Perestroika entities, controlled by Mr. Mohn, exercise shared voting and dispositive power over a significant ~10.1% stake, while Mr. Mohn retains small sole holdings and vested RSU rights. The conversion of exchangeable bonds to equity and incremental purchases over 2024–2025 altered ownership composition but not the aggregate Share count materially for the Reporting Persons. The filing is procedurally complete, replacing Item 1 and updating Item 3 and Item 5 to reflect these transactions and current voting/dispositive arrangements.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 8)

TRANSOCEAN LTD.

(Name of Issuer)

Shares, $0.10 par value

(Title of Class of Securities)

H8817H100

(CUSIP Number)

c/o Daniel Ro-Trock
Turmstrasse 30,
Steinhausen, V8, CH-6312
41 41 749 0500

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

09/30/2025

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

SCHEDULE 13D

CUSIP No. H8817H100

1

Name of reporting person

Frederik W. Mohn

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

OO

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

NORWAY

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 343,407.00
8	Shared Voting Power 95,074,894.00
9	Sole Dispositive Power 343,407.00
10	Shared Dispositive Power 95,074,894.00

11

Aggregate amount beneficially owned by each reporting person

95,418,301.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

10.1 %

14

Type of Reporting Person (See Instructions)

IN

Comment for Type of Reporting Person:

(1) See Item 3 for additional information regarding the source of funds reported in Row (4). (2) The amounts reported in Row (7) and Row (9) include (a) 22,148 Shares individually owned by Mr. Mohn and (b) 321,259 Shares issuable in relation to vested restricted share units Mr. Mohn has the right to receive based upon his service as a director of the Issuer. (3) The amounts reported in Row (8), Row (10) and Row (11) include 95,074,894 Shares owned by Perestroika (Cyprus) Ltd. (4) The percentage reported in Row (13) is based upon the 943,124,986 Shares outstanding as of July 29, 2025, as disclosed by the Issuer in the Issuer's Quarterly Report on Form 10-Q filed with the U.S. Securities and Exchange Commission on August 5, 2025.

SCHEDULE 13D

CUSIP No. H8817H100

1

Name of reporting person

Perestroika AS

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

OO

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

NORWAY

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 95,074,894.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 95,074,894.00

11

Aggregate amount beneficially owned by each reporting person

95,074,894.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

10.1 %

14

Type of Reporting Person (See Instructions)

CO

Comment for Type of Reporting Person:

(1) See Item 3 for additional information regarding the source of funds reported in Row (4). (2) The amounts reported in Row (8), Row (10) and Row (11) include 95,074,894 Shares owned by Perestroika (Cyprus) Ltd. (3) The percentage reported in Row (13) is based upon the 943,124,986 Shares outstanding as of July 29, 2025, as disclosed by the Issuer in the Issuer's Quarterly Report on Form 10-Q filed with the U.S. Securities and Exchange Commission on August 5, 2025.

SCHEDULE 13D

CUSIP No. H8817H100

1

Name of reporting person

Perestroika (Cyprus) Ltd

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

OO

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

CYPRUS

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 95,074,894.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 95,074,894.00

11

Aggregate amount beneficially owned by each reporting person

95,074,894.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

10.1 %

14

Type of Reporting Person (See Instructions)

CO

Comment for Type of Reporting Person:

(1) See Item 3 for additional information regarding the source of funds reported in Row (4). (2) The percentage reported in Row (13) is based upon the 943,124,986 Shares outstanding as of July 29, 2025, as disclosed by the Issuer in the Issuer's Quarterly Report on Form 10-Q filed with the U.S. Securities and Exchange Commission on August 5, 2025.

SCHEDULE 13D

Item 1.	Security and Issuer
(a)	Title of Class of Securities: Shares, $0.10 par value
(b)	Name of Issuer: TRANSOCEAN LTD.
(c)	Address of Issuer's Principal Executive Offices: Turmstrasse 30, Steinhausen, SWITZERLAND , CH-6312.
Item 1 Comment: This Amendment No. 8 to Schedule 13D (this "Amendment") amends the statement on Schedule 13D previously jointly filed by Frederik W. Mohn ("Mr. Mohn"), Perestroika AS, a Norwegian private limited company ("Perestroika AS"), Perestroika (Cyprus) Ltd., a Cyprus private limited company and a wholly owned subsidiary of Perestroika AS ("Perestroika Sub" and together with Perestroika AS, "Perestroika"), with the U.S. Securities and Exchange Commission on December 19, 2022, as previously amended (the "Prior Schedule 13D"). As used herein, "Reporting Persons" refers to Mr. Mohn, Perestroika AS and Perestroika Sub. Unless set forth in this Amendment, all Items are unchanged from the Prior Schedule 13D. Capitalized terms used and not defined herein shall have the meanings ascribed to them in the Prior Schedule 13D. Item 1 is deleted in its entirety and replaced with the following: This statement on Schedule 13D (as amended, this "Statement") relates to the shares, par value $0.10 per share (the "Shares"), of Transocean Ltd., a company organized under the laws of Switzerland (the "Issuer"). The Reporting Persons directly or indirectly hold Shares in the Issuer. The principal executive offices of the Issuer are located at Turmstrasse 30, CH-6312 Steinhausen, Switzerland.
Item 3.	Source and Amount of Funds or Other Consideration
	Item 3 is hereby amended by adding the following: On April 21, 2023, Perestroika Sub exchanged $213,367,000 aggregate principal amount of 2.5% Senior Guaranteed Exchangeable Bonds due January 2027 (the "2.5% Exchangeable Bonds") pursuant to the terms of that certain Indenture, dated as of August 14, 2020, among Transocean International Limited (formerly known as Transocean Inc.), the Issuer and certain subsidiary guarantors, and Computershare Trust Company, N.A., as successor trustee to Wells Fargo Bank, National Association (the "Exchange Transaction"). The 2.5% Exchangeable Bonds were issued by Transocean International Limited (formerly known as Transocean Inc.), a wholly owned subsidiary of the Issuer and exchangeable into Shares at an initial exchange rate of 162.1626 Shares per $1,000 principal amount of 2.5% Exchangeable Bonds. This transaction represented a change in the form of the Reporting Persons' beneficial ownership, but did not change the overall amount of Shares beneficially owned. On September 15, 2023, in connection with the acquisition of all of the issued and outstanding equity interests in Liquila Ventures Ltd. ("Liquila"), the Issuer delivered 1,978,396 Shares valued at $15,870,000 for the equity interests of Liquila owned by Perestroika Sub. On February 27, 2024, Perestroika Sub purchased 1,000,000 Shares at a price of $4.89 per Share. On May 15, 2024, Perestroika Sub purchased 2,000,000 Shares at a price of $6.01 per Share. On August 2, 2024, Perestroika Sub purchased 2,000,000 Shares at a price of $5.23 per Share. On September 12, 2024, Perestroika Sub purchased 1,500,000 Shares at a price of $4.13 per Share. On September 26, 2025, Perestroika Sub purchased 4,000,000 shares at the public offering price of $3.05 per share in connection with a registered public offering of securities by the Issuer, as described in the Issuer's prospectus supplement filed with the U.S. Securities and Exchange Commission on September 26, 2025. Each of these purchases was made using cash from Perestroika's ongoing operations.
Item 5.	Interest in Securities of the Issuer
(a)	Item 5 is deleted in its entirety and replaced with the following: The aggregate number and percentage of Shares (including Shares issued upon the Exchange Transaction) beneficially owned by the Reporting Persons are as follows (based upon the 943,124,986 Shares outstanding as of July 29, 2025, as disclosed by the Issuer in the Issuer's Quarterly Report on Form 10-Q filed with the U.S. Securities and Exchange Commission on August 5, 2025): (i) Mr. Mohn beneficially owns 95,418,301 Shares, or approximately 10.1%. (ii) Perestroika AS beneficially owns 95,074,894 Shares, or approximately 10.1%; and (iii) Perestroika Sub beneficially owns 95,074,894 Shares, or approximately 10.1%.
(b)	Mr. Mohn has: (i) sole power to vote or direct the vote of 343,407 Shares; (ii) shared power to vote or direct the vote of 95,074,894 Shares; (iii) sole power to dispose or direct the disposition of 343,407 Shares; and (iv) shared power to dispose or direct the disposition of 95,074,894 Shares. Perestroika AS has: (i) sole power to vote or direct the vote of 0 Shares; (ii) shared power to vote or direct the vote of 95,074,894 Shares; (iii) sole power to dispose or direct the disposition of 0 Shares; and (iv) shared power to dispose or direct the disposition of 95,074,894 Shares. Perestroika Sub has: (i) sole power to vote or direct the vote of 0 Shares; (ii) shared power to vote or direct the vote of 95,074,894 Shares; (iii) sole power to dispose or direct the disposition of 0 Shares; and (iv) shared power to dispose or direct the disposition of 95,074,894 Shares.
(c)	Except as described in Item 3 above, there have been no reportable transactions with respect to the Shares within the last 60 days by the Reporting Persons.
(d)	Except as set forth herein, no other person is known by the Reporting Persons to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, Shares and Exchangeable Bonds beneficially owed by the Reporting Persons.
(e)	Not applicable.

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.

Frederik W. Mohn

Signature:	/s/ Frederik W. Mohn
Name/Title:	Frederik W. Mohn
Date:	09/30/2025

Perestroika AS

Signature:	/s/ Frederik W. Mohn
Name/Title:	Chairman and Sole Director
Date:	09/30/2025

Perestroika (Cyprus) Ltd

Signature:	/s/ Frederik W. Mohn
Name/Title:	Director
Date:	09/30/2025

FAQ

What percentage of Transocean Ltd. (RIG) do the Reporting Persons own?

The Reporting Persons beneficially own approximately 10.1% of Transocean Ltd.'s outstanding shares based on 943,124,986 shares outstanding as of July 29, 2025.

How many shares does Frederik W. Mohn personally control or own?

Mr. Mohn beneficially owns 95,418,301 shares in the aggregate, with sole voting/dispositive power over 343,407 shares and shared voting/dispositive power over 95,074,894 shares.

What significant transactions changed the Reporting Persons' holdings?

Key transactions include the April 21, 2023 exchange of $213,367,000 principal of 2.5% Exchangeable Bonds into Shares and multiple cash purchases in 2024–2025, including 4,000,000 shares at $3.05 per share on September 26, 2025.

Did the Reporting Persons use debt or operational cash to buy shares?

The filing states each of the disclosed purchases by Perestroika Sub was made using cash from Perestroika's ongoing operations.

Does the filing disclose any legal proceedings related to these holdings?

No; the Schedule 13D/A does not disclose any legal proceedings related to the holdings.