A group of people take a cruise on a ramshackle yacht off the Florida coast. The engines stalls for the second time and there's this really weird tinge to the sky, like just before a tornado. Deep below an old sunken ship begins to bubble. Later that night they almost run into that same ship. The following morning the boat is on a reef and sinking so they must go to the nearby island. At first it seems deserted but they see a building, an old motel. They soon learn they aren't the only inhabitants--there's a creepy old German guy (Peter Cushing) who wants to know why they have trespassed in his home. He's a former SS Commander. He's very concerned that they saw a ship off the island so he goes to investigate and sees it in the distance. This makes him very nervous. It's because the ship's occupants have awakened and make their way to the island. These are albino looking guys in Nazi uniforms, part of an experiment from World War II that has survived. What makes them really creepy is that they are utterly silent and kill with their bare hands. There's no flesh-eating here, just murder.
The main characters are tourist Rose (Brooke Adams) and deckhand Keith (Luke Halpin), with the story told in a wraparound that ends how it begins, sort of the same device used in LET'S SCARE JESSICA TO DEATH and ATTACK OF THE MUSHROOM PEOPLE. SHOCK WAVES is the best Nazi zombie movie ever.