You have to go to great lengths to marry the merman of your dreams.
Xanda has the right idea: "I live in Hawaii, so what better way to trash the dress, than to swim in it?"
The dress isn't gonna trash itself, you're gonna have to do a little of the work.
My friend can still fit into her wedding dress from 1985. For her 25th anniversary, she celebrated by hiring a photographer to take pictures of how ridiculous the dress is, and how awesome it is to trash it.