RIG Transocean Ltd

2

3

4

This Amendment No. 1 to Schedule 13D (this “ Amendment ”) relates to the shares, par value CHF 0.10 per share (the “ Shares ”), of Transocean Ltd., a company organized under the laws of Switzerland (the “ Issuer ”). This Amendment amends the statement on Schedule 13D previously jointly filed by Frederik W. Mohn (“ Mr. Mohn ”) and Perestroika AS, a Norwegian private limited company (“ Perestroika ”) with the Securities and Exchange Commission on February 5, 2018 (the “ Prior Schedule 13D ”).  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.

The Reporting Persons (as defined below) are filing this Amendment to report the transfer of Shares directly owned by Perestroika to Perestroika (Cyprus) Ltd., a Cyprus private limited company and a wholly owned subsidiary of Perestroika (“ Perestroika Sub ”).

Item 2.                                                          Identity and Background

Item 2 is deleted in its entirety and replaced with the following:

This Schedule 13D is filed jointly by (i) Mr. Mohn, a citizen of Norway, (ii) Perestroika, a Norwegian private limited company, and (iii) Perestroika Sub, a Cyprus private limited company (together with Mr. Mohn and Perestroika, the “ Reporting Persons ”).

The address of the principal business office of each of Mr. Mohn and Perestroika is Statsminister Michelsensvei 38, 5320 Paradis, Norway.  The address of the principal business office of Perestroika Sub is c/o Pwc, Karaiskaki 6, City House, 3032 Limassol, Cyprus.

Mr. Mohn’s present principal occupation or employment is (i) serving as the sole owner and managing director of Perestroika, which is primary engaged in the business of investing in oil and gas, shipping, infrastructure, real estate development and financial services entities, and (ii) serving as a director of the Issuer.  The principal business of Perestroika Sub is investing in companies associated with oil and gas, shipping, finance and real estate.

The name, citizenship, business address and present principal occupation or employment of each director and executive officer of Perestroika Sub are listed on Schedule A attached hereto and incorporated herein by reference.

None of the Reporting Persons, during the last five years, been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors) or been party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceedings was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.

Item 3.                                                          Source and Amount of Funds or Other Consideration.

Item 3 is hereby amended by adding the following:

On March 1, 2018, Perestroika purchased 1,000,000 Shares at a weighted average price of $9.2786 per Share.  On March 2, 2018, Perestroika purchased 1,000,000 Shares at a weighted

5

average price of $9.3049 per Share.  Each of these purchases were made using cash from Perestroika’s ongoing operations.

On March 16, 2018, Perestroika transferred 32,436,351 of its Shares and all of its Exchangeable Bonds to Perestroika Sub at a price of $9.54 per Share and 100% of the principal amount of Exchangeable Bonds transferred.  Each of these purchases were made using cash from Perestroika Sub’s ongoing operations.  These purchases represent a change in the form of Mr. Mohn’s and Perestroika’s beneficial ownership, but do not change the overall amount of Shares or Exchangeable Bonds beneficially owned by Mr. Mohn or Perestroika.

Item 5.                                                          Interest in Securities of the Issuer.

Item 5 is deleted in its entirety and replaced with the following:

(a)                                  The aggregate number and percentage of Shares (including Shares issuable upon the exchange of the Exchangeable Bonds at the Initial Exchange Rate) beneficially owned by the Reporting Persons are as follows (based upon 461,715,265 Shares outstanding as of April 24, 2018 as disclosed by the Issuer in the Issuer’s Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on May 1, 2018):

(i)                                      Mr. Mohn beneficially owns 67,740,289 Shares, or approximately 13.6%.

(ii)                                   Perestroika beneficially owns 67,696,433 Shares, or approximately 13.6%.

(iii)                                Perestroika Sub beneficially owns 67,036,433 Shares, or approximately 13.5%.

(b)                                  Mr. Mohn has:

(i)                                      sole power to vote or direct the vote of 43,856 Shares;

(ii)                                   shared power to vote or direct the vote of 67,696,433 Shares;

(iii)                                sole power to dispose or direct the disposition of 43,856 Shares; and

(iv)                               shared power to dispose or direct the disposition of 67,696,433 Shares.

Perestroika has:

(i)                                      sole power to vote or direct the vote of 0 Shares;

(ii)                                   shared power to vote or direct the vote of 67,696,433 Shares;

(iii)                                sole power to dispose or direct the disposition of 0 Shares; and

(iv)                               shared power to dispose or direct the disposition of 67,696,433 Shares.

6

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 67,036,433 Shares;

(iii)                                sole power to dispose or direct the disposition of 0 Shares; and

(iv)                               shared power to dispose or direct the disposition of 67,036,433 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 owned by the Reporting Persons.

(e)                                   Not applicable.

Item 7.                                                          Material to be Filed as Exhibits.

Exhibit I                                                  Joint Filing Agreement among the Reporting Persons, dated as of June 15, 2018.

7

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.

Dated: June 15, 2018

8

Schedule A

Directors and Executive Officers of
Perestroika (Cyprus) Ltd.

The following table sets forth certain information with respect to the directors and executive officers of Perestroika (Cyprus) Ltd.  The business address of each director and executive officer of Perestroika (Cyprus) Ltd. is c/o Pwc, Karaiskaki 6, City House, 3032 Limassol, Cyprus.

9