A very tired-looking Errol Flynn heads the cast of Maru Maru. Flynn plays deep-sea diver Gregory Mason, who is hired to locate a sunken PT boat bearing a diamond-encrusted religious icon. Mason's employer on this mission is the disreputable Brock Benedict (Raymond Burr), a firm believer in the old buccaneer credo that "dead men tell no tales." Aware that he's expendable once he finds the treasure, Mason stalls as long as he can, hoping that Benedict and his crooked flunkies will end up wiping out one another. He also intends to claim the treasure for himself, rather than turn it over to the proper authorities. Ruth Roman co-stars as Stella Callahan, the widow of Mason's former partner, who wants nothing more than for Mason to return the gem-studded cross to its rightful owners (well, maybe she wants Mason, too).
by Hal Erickson synopsis