Detective Comics #7

Slam gets a telegram asking him to fly to Atlantic City immediately. On arrival Slim and Shorty discover that the man who sent the telegram has just drowned, so to investigate disguise themselves as life guards. He saves Ethel Mann from drowning, and later gets a message asking if they can meet. She claims to be a excellent swimmer, but claims to have been pulled underwater by a pair of non-human arms. Shorty gets pulled into the sea by a mysterious inhuman figure, but Slam saves him. Later, when saving Ethel yet again, the \"creature\" is revealed to be merely a man in a diving suit.