A group of people descend into the depths of the ocean to only have their cables on their underwater diving bells snap. Prompting to the depths of the ocean, the group is believe to be dead by the crew on top and all hope in looking for them is pointless. Unbeknownst to them, the group is very much alive and are unharmed at the bottom of the ocean. Leaving the diving bell, the group of two men and two female make their way out and discover a network of underwater caverns. They encounter a shipwreck survivor in the caverns and he tells them his story of how he has been in the caverns for 14 years and there is no way out. Believing they will forever be stuck in the caverns, the men decide to venture the cavern and stumble across a volcanic vent that supplies the cavern with oxygen. Meanwhile back on the surface, Professor Millard Wyman, a scientist who designed the original diving bell, decides to try again to explore the depths of the ocean. He finds out that there is another diving bell in existence that is identical to the one that was lost.

Bruce Li discovers a hidden stash of gold while scuba diving, he and his friends divide it up between them. The gang who stole the gold track Bruce and his friends down one by one slowly getting back what they believe to be their property.

A scuba team, a marine archaeologist and a Mexican historian join forces to reach the wreck of an historic Spanish galleon before a well-armed commercial expedition does.