The idea is to spread out a convoy of seasteads in a long line so that one of them is near land. If the one near land can link to the Internet and they can all talk to each other, then they can all be on the Internet. Imagine 30 seasteads doing a migration while in a line with 30 miles between each, so the whole line would be 900 miles long. At any given time at least one of these should be near land and be able to link into the Internet. As long as all 30 can link together, then the whole group could have Internet even when some were very far from land.
This could let you use land base communications which might save money over a satellite based system. The downside is that you would need to have something worked out on each of the islands, unless there is a high speed Internet over cellphone, which there just might be soon.