The sea-dragons or waterworms of Drexel were gigantic sentient reptiles who dwelt in the never-ending ocean of their world. They communicated with each other using ultrasonic signals.
When Governor Quarg’s scavengers arrived on Drexel, they set up a scheme where they used a sonic jammer to cause any passing spacecraft to malfunction and crash to the planet. But the jamming signal proved damaging to the Sea-dragons’ and prompted them to attack the scavengers. The scavengers’ technicians realized the damage their signals were causing and objected to their use, but their efforts were thwarted and they were exiled to the sea. But the technicians survived, and eventually developed a relationship with the Sea-dragons, and became to be known as the Dragon Lords, even though the relationship was between equals rather than one of servitude. As infants they resembled small lizards, and would spy on Quarg’s city-ship to report the scavengers’ intentions back to the Dragon Lords.