I’ve grinded from 0 skills and materials to building a boat on the prison island. It just requires some grinding to get access to the tools/materials that you need. There’ve been some significant changes to the island recently, so it’s much harder, now, but I’d imagine it isn’t impossible. It’s just, you know, a challenge start that’s meant to be difficult.
Many people who talk about it on discord just take high swim skill at the start and then restart until they find an island near the shore. That seems to be how the majority of people get off the island, but I think that’s really dumb, personally, and completely ignores the whole point of starting on the prison island.