You haven't missed anything! They changed the location and made it contemporary. Instead of a single hero, there is two couples. A lot more blatant violence where Lovecraft is understated. The only thing that really worked was the old drunk which was pretty much left untouched. What could potentially have been interesting is what Lovecraft never alludes to, even if that must have been present- that people may not have very willing to mate with fish people. But the Movie was just gross there.