The Deep Sea Dragon - S1.E5

A deep sea expedition discovers a huge pearl at the bottom of the ocean. When they are attacked by a sea monster they send out an S.O.S. Superboy and Krypto head to the ocean to rescue them, but discover that the sea creature is a dragon that was only attacking in order to protect the giant pearl which is really its egg. When the pearl is stolen by pirates, the sea creature gets angry. Superboy and Krypto capture the pirates and return the egg to the dragon.