I'm not sure what the point of living off the coast of SF is if you can't go in to land now and then. The whole point of being in SF is the networking possibilities, not some magical sphere of influence that surrounds the area.
If you still can't enter the country you might as well be in your own country working in comfortability.
A few weeks off on 'shoreleave' every couple months might be both practical and compliant with border controls.
Oil platform 'roughnecks' spend 2-4 weeks working 12-hour days, then get 2-4 weeks off on shore, for work that's much more physically draining and dangerous than tech work.
Not sure why you think they couldn't go to land. It is much easier to enter the US as a tourist or on a short-term visa than to get a work visa to live and work here. I think that coders living on a ship that isn't legally part of the US could still enter regularly on a tourist visa for meetings.
Think of the other direction - if you can't go on land (actually you can, but let's assume you couldn't), then folks from Silicon Valley can visit the ship. Project managers can sync periodically with developers on the ship, fellow developers can be sent on the ship for training sessions etc.
Working in your own country just doesn't seem to produce the amount of innovation that happens in Silicon Valley. Otherwise, we should be able to see lots of successful geographically-distributed startups made of software developers who use teleconferencing and other online tools. While that does happen with many open-source projects, it doesn't seem to work as well for commercial ventures.
If you still can't enter the country you might as well be in your own country working in comfortability.