Re: " and releases no discharge into the surrounding waterway"
"And what about heat?
Like extra heat into already warming up oceans?"
You can work it out. Some assumptions:
10 of these 50MW data centres, all off the coast of Texas in the gulf of Mexico. Let's assume all the electricity consumed goes into heating the gulf's water.
10x50MW is equal to 1.6x10¹⁶ J per year.
Volume of the gulf is 2.4 million cubic kms, or about 2.4x10¹⁸ kgs of water.
Specific heat capacity of water is about 4200 J/kg/°C
So the temperature increase of the gulf over a year is 1.6x10¹⁶ / (2.4x10¹⁸ x 4200).
It's about 0.0000016°C per year.
To put it in some context, if we assume that the gulf receives the same solar radiation per unit area as the rest of the world (averaged out for day/night cycles) then the 500MW of electrical power is only about one millionth that of the solar radiation.
Of course, that energy will be localised, not spread out across the whole gulf. But if you want to think about the effect on weather, do the same calculation over say, just the area of a weather region. But that's getting into meteorology and I'm way out of my depth now.