The Deepest Dive

The crew of Sealab are testing a new submersible vehicle called the ""Crystal Ball"", which is made out of mostly glass and is supposed to be better than conventional submersibles and dive deeper. They are given a mission to place a seismograph unit at the bottom of a deep part of the sea, but for some reason the unit stops functioning. They go back out with a second replacement seismograph unit and realize that a giant squid had taken the first unit and used it for material for its rock home. The squit catches the Crystal Ball and the crew is stuck trying to escape from it's grasp. They eventually get free and the new seismograph unit works.