Hmmm... Don't you need to beat Alexander and the Worm at the end before you're allowed to use the boat? Or are you saying you can sneak to the boat and escape without fighting?
They could always chain the boat up with a magic padlock and have Alexander drop the key.
No, that is just one way off the island.
The earliest you unlock inside the fortress (that I am aware of) to admit, I didn't do it so for all I know it crashes or just goes to another part of the island.
