Which movie has a man who turns into an octopus or aquatic creature in the end?

Far fetched, but I saw a movie I think from the early 90's or 80s that had the very end one of the main, if not THE main, character turn into an octopus or some sort of aquatic creature at the end. I could be wrong, but the only scene I vaguely remember is maybe a woman at the end saying something to him while he's in a tank of water. Bad memory in this one, but I'd really like the help if anyone knows. I'd love to see it again. Thanks!