[tim333]

I can't see any reason to put them underwater rather than in a field somewhere. I think the space rationale is you may run out of fields.

[droopyEyelids]

Placing them underwater means you get free, unlimited cooling.

Exactly the opposite of space, where all cooling must happen through radiation, which is expensive/inefficient

[queenkjuul]

It's not free cooling underwater, you still have to circulate the water and seal the components.

Makes far more sense to build on the beach than underwater, if all you want is unlimited sea water to pump around.

[yencabulator]

I understood that part of Microsoft's experiment was to see how being hermetically sealed would affect hardware durability. Submerging is a good way to demonstrate the seal, but that part might have been just showmanship.