Nothing on the scale of the Piper Alfa disaster, but on a drillship I was Capt. on in 1978-80 we lost a diver due to a silly request from the “Company man” to send divers down “to check the water depth”
This while we were in the process of running anchors and without consulting me.
The wire parted and the diving bell inside fell to the bottom, with two divers.
We managed to get both up and into decompression, but one died.
PS> Not involved in the accident, but I was Marine Advisor onboard the “DB29” before she sunk off Hainan, China in 1991: