I like the idea of low speed submersible mixers as thrusters. The thrusters have large propellers, like 6 feet (2 meters), that turn slowly. The motors are like 2 to 10 Hp (1.5 kw to 7.5 kw) but the thrust can be 200 to 1000 lbs. So the electricity is low enough to be powered by solar. See here, or here. These have lots of thrust but since they turn slow the top speed may only be 2 or 3 MPH. We will have 4 of these, so probably each one can be very low power, like 1.5 kw or 2.5 kw. Also, the propeller size might be 5 foot, not the largest sizes, and maybe not the lowest speeds.
These use low enough power that solar could drive these all day long. In the Caribbean you could usually get to another country in a day. If you are playing on the Internet you probably don't care how long it takes anyway. But when moving slow on the ocean you must take extra care to get enough stability to be comfortable.
We will have to plan for currents though. If we are going against a current that is faster than the seastead, that would be a problem. It seems there are so many edies that with the right plan we could be ok. This will be something to figure out though.
Go to seastead.ai.