The sea creatures were the disguises of dive-masters Thorn and Dahlia. The sea creatures were green monsters with both reptilian and fish-like qualities. They had glowing yellow eyes and razor sharp teeth. They behaved like typical predatory animals, but did show occasional bouts of intelligence. They were particularly aggressive, as one of them tried to drown Mystery Inc. by bashing in the windows of the mystery machine. They were incredibly skilled swimmers and were shown to be quite strong, as one of them was able to punch straight through a glass window.