Arvid Nelson

A merchant is found hanged in his office and only Matt thinks it was murder.

During a shark-filming expedition, Brent Marshall's flirtatious wife pays him no attention, concentrating instead on Mike Nelson and two camera operators. Enraged, Marshall severs a camera cage cable and drops his three 'rivals' into shark-filled waters.

An electronic test boat sinks, taking a newly-developed guided missile tracker with it to the bottom of the sea. Mike Nelson, hired to recover the invaluable equipment, discovers skin-diving thieves have already made off with it.

Prison escapees search out third partner holding their loot.