I stand by my suggestion that he bored the holes from the inside.

I agree that the abillity to swim was unusual at the time and may also have been in his favour.

I would presume that the enemy ship would have been spotted approaching and so it was not a case of overtaking the enemy ship. Judging by the description of the enemy crew's activites they would have been waiting overnight for daylight to commence their attack. This would also help him sneak aboard.

That's a lot of assumptions, but so is a lot of what is on this thread!

Robin