The wild success of "Jaws" spawned a number of cheap imitators as Hollywood rushed to fill the water with various overblown species of terror.
One of the first to emerge was "Orca" which boasted a huge killer whale as the evil bikini-devouring monster. While it did boast the charms of Bo Derek, some good photography, and a score by Ennio Morricone, it was a waterlogged mess.
Also out in 1977 came "The Deep". Starring Nick Nolte and Jacqueline Bisset this film wasn't cheap but it did suffer from a bargain basement script written by Peter "Jaws" Benchley that omitted any tension whatsoever. The malevolent beastie this time was a horrible eel-like creature with teeth aplenty although it got precious little screen time.
The most entertaining of the underwater flicks is "Piranha" from the fabulous New World Studios of Roger Corman. Directed by Joe "Gremlins" Dante this highly entertaining tongue-in-cheek effort sees a slew of flesh-lovin' Piranha released into a river from the laboratory of deranged scientist Kevin McCarthy. Lots of typical Dante touches include a high body count and a very 50s slant on the proceedings. It later inspired a sequel directed by James Cameron and had nothing to do with "Piranha Women" starring Shannon Tweed.
Most recently we've been treated to "Shark Attack" (1999) from Nu Image. The budget for this straight-to-video flick is obviously limited but every penny is up there on the screen. Plenty of well-timed explosions and underwater shark shots keep things moving along nicely. And with "Shark Attack 2" in production it looks as if there'll be cheap underwater thrills around for some time to come.