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