I remember watching some late-night episode of a U.S. sci-fi program when I was a kid in the 1990's, here in the UK. I'm pretty sure the episode was made in the 90's too.
What I remember of the episode is that it involved a scientist who was modifying himself, gradually it got out of control and he ended up with gills and was sort of monster-like.
I thought it might be from Tales From The Crypt, but I can't find an episode matching that plot. Any suggestions on what show this could be from would be gratefully received! :-)