it’s because a hurricane comes and destroys literally every other boat in the harbor, so there’s no competition 😛
they survive because Lt. Dan is Lt. Dan and wants to be out at sea during the storm so that he can yell at the storm to “come and get him”
I’m sure a lot of people do remember this, but it’s kind of fun to see the pretty key plots points that I did not retain from whenever i first watched this movie