Preparing for a well-earned two-week vacation, Clark Kent says goodbye to Lois and Jimmy. What they do not realize however, is that even though "Clark" is taking some time off, he will still be active as Superman.

While flying across the Atlantic, Superman spots a rocket ship that slams into the ocean. Investigating, he finds two mer-people trapped inside. Superman tears the metal door off, allowing the man and the woman to swim free. The man introduces himself as Vul-Kor and his companion is his daughter Lya-La. As the two alien mermaids cannot breathe normal air, Superman decides to exile himself undersea to help them acclimate. He uses nameplates from sunken vessels to create a floating message to explain his absence. A passing mariner finds the signs and alerts the world that Superman is now living under the sea...