Space gets you 24/7 solar power. To run a data center for 12 hours without sunlight, you'd need massive batteries. Also oceans have weather and corrosion.

The issue with putting stuff in space isn't the kinetic energy required. In LEO that's about 30 megajoules per kilogram or $5 worth of propellant. The issue is that orbital launch vehicles are not reusable, so you must destroy an expensive rocket to get your payload to orbit. All of these space datacenter efforts are betting that Starship will be fully reusable.

You can't just sea-stead your way to it though, salt water + network accessibility + literal piracy + how much data you can move + the environmental toll of doing much of anything on the see = equally crazy challenges with more laws that can stop you.

By the time you got permission to lay all the cables you'd need to lay, etc. your competition would already be done with their space data center, or Lunar one in a peak of eternal sunshine or whatever. This is a race to the most compute. Whoever gets the most geniuses in their "country of geniuses in a datacenter" wins.

Wins what? Well, everything they want effectively forever.