Up From the Depths (1979) takes place on a Hawaiian beach where tourists, locals and biologists alike are being terrorized by a giant shark-like creature. Okay, right from the bat, you should be thinking "Jaws knock off," and quite frankly, you've pretty much hit the nail on the head.
There are several groups of characters in this film that all have different reactions to the threat. One one side of the spectrum is the hotel staff who are trying to convince their customers that nothing is wrong, and when they can't hide the deaths any longer convinces everyone on the island to sail out and kill the beast for a hefty reward. On the other end is a company of marine biologists located near the hotel who are cataloging the different kinds of fish found in the area. Needless to say, once they know the creature is out there, they want to preserve the killing beast for scientific study.
Stuck between these two extremes are a pair of grifters who convince tourists to hire them in order to take them on adventures and treasure hunts. Most of the time, these hunts do dig up buried treasures, they just happen to have been buried by the guides instead of being long-lost loot.
Overall, Up From the Depths isn't too inspiring of a film. While its not so bad as to go on the Worst Movies Ever list, it also doesn't quite fit the "so bad, it's good" list either. In the end, the story, acting and general quality of the movie is mediocre at best.
The other film in this double-feature, Demon of Paradise (1987), actually comes off worse than Up From the Depths. At least that film has some good scenery. While Demon of Paradise is supposed to take place at a lake in Hawaii, the feel of the set seems to come from areas like Florida or Louisiana.
In this movie, a lizard-man (that somehow has no problems breathing underwater, I might add) is released from a long hibernation through dynamite fishing and terrorizes a lakeside resort. As the local Sheriff and, yes another scientist, join forces to find out what is causing a string of deaths, they have to convince the resort owner that the monster they are tracking is real and not just a hoax.
The biggest problem with Demon of Paradise is that not a lot seems to really happen. Outside of the main plot involving the resort thinking the creature is a fake and the investigation of the creature itself, the plot follows some characters who are involved in the trafficking of illegal explosives. These would be the same explosives that lead to the creature waking up. This side plot seems like little more than a way to distract the Sheriff while the scientist tries to find proof of the monster and, of course, provide a few more bodies for the creature.
Like I said, Demon of Paradise just doesn't hold up to even the standards that Up From the Depths set, and that wasn't even a high bar. The only good thing I can say about this movie over the earlier one is that the monster isn't as cheesy looking. I mean, it's a guy in a rubber suit and there are plenty of times you can see the flesh under the mask, but it's better than a fin breaking the surface and some dark shapes under the water.
The only extra features this collection has are a group of classic Roger Corman trailers, plus the ability to play the two movies in grindhouse style. In other words, you can play the two movies back-to-back with those aforementioned trailers separating the two films. The only other extra is a making-of for Up From the Depths as the crew talks about their memories of working on the film. Corman is also interviewed and discusses what led his production company to making Up From the Depths as a follow-up to the company's first film, Piranha.
Unless you are a hardcore Roger Corman fan and looking to collect all of the films that come out in this Cult Classic collection, then Roger Corman's Cult Classics Double Feature: Up From the Depths / Demon of Paradise is better left behind. There are far better films to come out of this man's filmography to choose from than to waste the time, money and effort on this collection.