The current major roadblocks for any datacenter are, planning permissions, power connections, and cooling. The on a barge approach solves all of the above, unlike space which makes all of these problems worse.

Its power connections which is the major roadblock and as such obviously planning permissions get tricky because as we see in so many cases, so much grid electricity is used that that the planning permissions become tricky and rightfully so.

As many countries are now trying to suggest, bring your own power and we are happy.

So in that sense, Nuclear? sure, already being tried but not fast or big enough right now.

Sea? I don't think so. You literally get into murky waters on the future of the project and this part feels really hype based, atleast to me.

Perhaps some people feel that Sea could cool things off but in my understanding, if you already have nuclear, it would be better building Datacenters in colder stranded regions then to have really effective temperature/natural cooling.

Power is the core issue, Everything else is bolted on top of it in my opinion.