It's nice to see people try but the theory posted is obviously rubbish. The reason Desmond couldn't get away from the island is because the energy of the island (magnetism or whatever) affects the sea, this is why Michael had to sail in a specific direction and likely why the islanders raft drifted back to shore after it had been destroyed. I'd also suggest that it's why Henry Gale's balloon and the plane were drawn towards the island - in Henry's case though it may have been because of the Numbers or because of a previous mishap such as a system's failure.
This is why Fake-Henry says that God can't see the island any better than the rest of the world can. The Russians at the end of season 2 were obviously trying to find it and succeeded after the fail-safe caused enough of an energy release for it to show up on their computers.
The only theory I'll lay out there is that the island originally rose up. It would seem like the Black Rock got washed up onto the island, but I say that the island rose up while it was sailing over it. I've no idea why this would happen but it's just the sort of thing that the writers would trick us with.