The Coast Guard asks Mike to investigate the drowning death of a scientist who had invented a new type of rebreather.

Mike is trapped in a ""scubasphere"" when the cable attached to it snaps.

Mike investigates the source of a radar jamming signal that caused two ships to collide.

A famous newsman, convinced that he has a fatal illness, tries to end his life in such a way that his wife can collect his insurance, with Mike as a witness.

Unaware that two of his treasure-hunting friends are trapped inside, Mike sets charges to blow up a sunken ship that is a menace to a busy shipping lane.

A naval officer of a Caribbean nation is sabotaging a series of experiments Mike is conducting with the Coast Guard.