All Water-drakes were agile swimmers who were capable of moving at speeds of up to twenty knots (about twenty-one miles per hour). They moved almost silently and could squeeze through very small passages in reefs or cavern systems. Using its keen senses, including a sonar-like organ like that found in porpoises, it could locate its prey under the worst conditions. Then it striked with a burst of speed, as well as an uncanny sense of precision.
After successfully stalking a potential victim, the Water-drake could seize it with its six fin-claws or stun it with a blast of expelled water (treated as a waterbolt). Should either of these methods fail to make the victim tractable, the Water-drake could then try an attack with its large mouthful of multirowed, four-inch teeth. It used these to crush its prey into flexibility and then swallow it more or less whole. A larger victim could call for even more forceful methods: the long head and tail of the Water-drake made an effective whip or noose. (A larger Sea Serpent could even grapple and crush a small ship.)
Aside from the aforementioned fear of fire, the Water-drake's one weakness was its dislike of the disorienting effects of a stunning blow. Such an injury could cause the monster to flee.