In 1989 the UNOCAL owned Drillship Seacrest capsized in the Gulf of Thailand with the loss of 91 lives:
This is the third worst accident in the offshore oil & gas industry ever and an example of how the chain of command on a a drillship was/is totally compromised.
The long time Master on the Seacrest resigned shortly before this accident because his warnings about stability after she got a Topdrive installed, which involved raising the derrick and crown block, adding substantial weight high up. But without making any alteration to the Stability Booklet or the way the ship was operated and managed. (Largely by instructions from people in the UNIÒCAL office in Bangkok, with no maritime knowledge, or understanding and to the Toolpusher on board)
He was very experienced with this specific type of Drillships, having been at the building yard and taken first command of every one of the previous ships of this type build by Far East Livingston (FELS) at their yard in Singapore.
Seacrest was built as Scan Queen in 1977 as the last of a series of 5 small Drillships of same design and he stayed on that one.
He was replaced by a far less experienced Master that went down with the ship.
PS> I was Captain on the first one of the series, the Fredericksburg, in 1978-80. We drilled in the GoT together with Scan Queen in 1978. (But not for UNOCAL)