The Hardy's guided the motor boat out into the shark-infested ocean beyond the reef. Several times they saw sinister looking fins knifing through the sea around them. Suddenly Frank's blood ran cold - water was starting to pour in through a hole in the hull. They were sinking fast....... In the sultry heat of the West Indies, Frank and Joe hunt for a desperate gang of cargo thieves. But as the net tightens around the crooks, their tricks get nastier....