Transocean Ltd.
US ˙ NYSE ˙ CH0048265513

SecurityRIG / Transocean Ltd.
InstitutionCastleark Management Llc
Latest Disclosed Ownership837,120 shares
Latest Disclosed Value $ 5,550,106
Castleark Management Llc reports 26.68% decrease in ownership of RIG / Transocean Ltd.

On May 15, 2026 - Castleark Management Llc filed a 13F-HR form disclosing ownership of 837,120 shares of Transocean Ltd. (US:RIG) valued at $5,550,106 USD as of March 31, 2026. The entity filed a previous 13F-HR on February 12, 2026 disclosing 1,141,690 shares of Transocean Ltd.. This represents a change in shares of -26.68% during the quarter. The current value of the position is $5,173,402 USD.

Institutional Ownership: 13F and NPORT Filings

The Security and Class in the table below are shown exactly as filed by the investor. We do our best to track continuity of investments through acquisitions, and this will be reflected in the table as changes in names. In addition to descriptive data, performance of the investment is shown over time. To calculate quarterly performance, we first calculate cost basis of the shares purchased during the quarter, then use that to calculate gross profit. Quarterly return is Gross Profit / Starting Portfolio value.

Note that cost basis is calculated and stored in thousands, so small quarterly changes in shares frequently result in a cost basis of zero.

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Disclosed Equity Positions (from 13F/NPORT Filings)
File
Date		 Effective
Date		Form Security Class ID Avg Price
Paid (Est)		 Reported
Shares		 ΔShares ΔShares
(%)		 Reported
Value
(x1000)		 ΔValue
(%)		 Alloc
(%)		 ΔAlloc ΔAlloc (%) Cost Basis
(x1000)		 Unrealized
Gain/Loss
(x1000)
2026-05-15 2026-03-31 13F TRANSOCEAN REGISTERED SHS H8817H100 837,120 -304,570 -26.68 5,550 17.71 0.1836
2026-02-12 2025-12-31 13F TRANSOCEAN REGISTERED SHS H8817H100 1,141,690 1,141,690 4,715 0.1384
2025-02-18 2024-12-31 13F TRANSOCEAN REGISTERED SHS H8817H100 0 -679,750 -100.00 0 -100.00
2024-11-15 2024-09-30 13F TRANSOCEAN REGISTERED SHS H8817H100 679,750 470,950 225.55 2,889 158.55 0.1178
2024-08-14 2024-06-30 13F TRANSOCEAN REGISTERED SHS H8817H100 208,800 -208,800 -50.00 1,117 -57.40 0.0456
2024-05-16 2024-03-31 13F TRANSOCEAN REGISTERED SHS H8817H100 417,600 372,380 823.49 2,623 813.59 0.1091
2024-02-15 2023-12-31 13F TRANSOCEAN REG SHS H8817H100 45,220 -212,530 -82.46 287 -86.44 0.0127
2023-11-15 2023-09-30 13F TRANSOCEAN REG SHS H8817H100 257,750 257,750 2,116 0.1078
2019-08-13 2019-06-30 13F TRANSOCEAN REG SHS H8817H100 0 -420,400 -100.00 0 -100.00
2019-05-14 2019-03-31 13F TRANSOCEAN REG SHS H8817H100 420,400 205,580 95.70 3,662 145.61 0.1378
2019-02-12 2018-12-31 13F TRANSOCEAN REG SHS H8817H100 214,820 -272,500 -55.92 1,491 -78.07 0.0635
2018-11-14 2018-09-30 13F TRANSOCEAN REG SHS H8817H100 487,320 0 0.00 6,798 3.79 0.1953
2018-08-15 2018-06-30 13F TRANSOCEAN REG SHS H8817H100 487,320 475,720 4,101.03 6,550 5,595.65 0.2016
2018-05-14 2018-03-31 13F TRANSOCEAN REG SHS H8817H100 11,600 0 0.00 115 -7.26 0.0036
2018-02-15 2017-12-31 13F TRANSOCEAN REG SHS H8817H100 11,600 0 0.00 124 -0.80 0.0037
2017-11-15 2017-09-30 13F TRANSOCEAN REG SHS H8817H100 11,600 0 0.00 125 31.58 0.0039
2017-08-15 2017-06-30 13F TRANSOCEAN REG SHS H8817H100 11,600 0 0.00 95 -34.03 0.0031
2017-05-15 2017-03-31 13F TRANSOCEAN REG SHS H8817H100 11,600 0 0.00 144 -15.79 0.0045
2017-02-15 2016-12-31 13F TRANSOCEAN REG SHS H8817H100 11,600 0 0.00 171 37.90 0.0055
2016-11-15 2016-09-30 13F TRANSOCEAN REG SHS H8817H100 11,600 0 0.00 124 -10.14 0.0038
2016-08-10 2016-06-30 13F TRANSOCEAN REG SHS H8817H100 11,600 0 0.00 138 30.19 0.0044
2016-05-17 2016-03-31 13F TRANSOCEAN REG SHS H8817H100 11,600 0 0.00 106 -26.39 0.0033
2016-02-17 2015-12-31 13F TRANSOCEAN REG SHS H8817H100 11,600 0 0.00 144 -4.00 0.0043
2015-11-17 2015-09-30 13F TRANSOCEAN REG SHS H8817H100 11,600 0 0.00 150 -19.79 0.0048
2015-08-17 2015-06-30 13F TRANSOCEAN REG SHS H8817H100 11,600 -11,600 -50.00 187 -45.00 0.0050
2015-05-15 2015-03-31 13F TRANSOCEAN REG SHS H8817H100 23,200 11,600 100.00 340 59.62 0.0082
2015-02-10 2014-12-31 13F TRANSOCEAN REG SHS H8817H100 11,600 11,600 0.00 213 0.0055
2014-11-17 2014-09-30 13F TRANSOCEAN REG SHS H8817H100 0 0 0 0.0000
2014-08-15 2014-06-30 13F TRANSOCEAN REG SHS H8817H100 0 0 0 0.0000
2014-05-20 2014-03-31 13F TRANSOCEAN REG SHS H8817H100 0 0 0 0.0000
2014-02-20 2013-12-31 13F TRANSOCEAN REG SHS H8817H100 0 -11,600 -100.00 0 -100.00
2014-11-21 2013-09-30 13F/A-1 TRANSOCEAN REG SHS H8817H100 11,600 -16,100 -58.12 371 -72.06 0.0105
2013-09-26 2013-06-30 13F TRANSOCEAN REG SHS H8817H100 27,700 27,700 1,328 0.0441
Legend
Shares
The total number of shares held by the institution at the end of the reporting period (the effective date). This is provided in the filing.
Value
The total value of the shares as of the effective date. This is provided in the filing.
Avg. Share Price
The weighted average share price of the shares held by the institution. We use FIFO accounting to determine this price
Class
This is the security class as indicated by the filer. There are a variety of values for this field. Common values include "EC" = equity common, "EP" - equity preferred
Allocation (%)
The percent of the institution's portfolio that this position represents. This is provided in NPORT filings. For 13F filings, we calculate it.
Change in Allocation
The change in allocation from the prior reporting period. This is calculated as current allocation - prior allocation.
Change in Allocation (%)
The percent change in allocation from the prior reporting period. This is calculated as (current allocation - prior allocation) / prior allocation.
Cost Basis
The total cost of the shares held. This is calculated as reported shares * avg. share price
Unrealized Gain/Loss
This is the market value of the position as of the effective date minus the cost basis.