The point of placing a container data center cooled with sea water at the shore is that, they are still readily available for maintenance. In the deep ocean, maintenance becomes a headache. Either someone lives there and does the maintenance. Or you fly people there regularly to do the maintenance. Like how they do it with ocean platform oil rigs. Cooling with seawater requires more maintenance, descaling, valve replacements, animal growth removal, divers, helicopters, camera drones, etc. Oil rigs can justify the cost with the extremely high profit margins that oil generates. I don't think data centers can justify such a expense. Specially now the bubble is starting to deflate and trillions of dollars have already been drained.