A red alert is signaled after a supply ship's concrete mooring, cast off during a hurricane, unwittingly strikes Sealab's control dome and splits a major section of the shell.

The crew of Sealab ventures into the frozen Arctic to rescue two scientists who have been trapped by a blizzard while on a scientific expedition.

A new world opens up for Roger Cummings, a disabled boy whose father is doing research at Sealab, when Bobby befriends him and teaches him how to dive.

The entire Sealab complex is threatened by an increasing buildup of aggressive sharks in the area.

An archaeologist enlists the aid of Hal, Ed, and Gail in removing ancient Mayan gold artifacts buried in the hold of a vessel sunk during WWI.

Human complications make dealing with the mechanical ones more difficult when cargo sub "Aquarius" crashes into Seamount and endangers the Sealab complex.

An earthquake spells danger for Sealab when the recurring mass of shock waves ruptures exposed canisters of radioactive waste.

When a space probe loses its parachute during reentry and plummets out of sight into the ocean's depths, the staff of Sealab is called on to locate it.

Hal, Ed, and Gail plunge to the lowest depths of the ocean in a special crystal bell to plant a second seismographic signaling device after the first one mysteriously disappears.

Ed, Gail, and Hal become "muckrakers" when ocean waters around Sealab become blanketed with layers of loosened silt

An approaching red tide has more than the fish in a panic - the murky oceanic flux, which initiates a process of oxygen depleting, could cut off the life support system of Sealab.

Ed considers resigning from Sealab after Dr. Williams grants permission to a submarine geologist to use explosives on Seamount for the purpose of oil exploration.

Although the Sealab crew doesn't like helping Mr. Harlan trap two animals from every species on the Seamount for a new aquarium, they carry out the task because of orders.