Round-bodied beetles found in deep fresh water, attracted by vibrations or noise
These round-bodied beetles are found in bodies of fresh water of at least 30 feet deep, preferring lakes or slow-moving rivers. They are always hungry and are attracted by vibrations or noise.
Basic Fantasy Field Guide Omnibus
Omnivorous aquatic beetle that hunts by scent and vibration
Hunting by scent and vibration, and dwelling in fresh water at least 30-ft deep, the water beetle is a powerful threat to the unwary adventurer. Omnivorous and insatiable, the water beetle will consume whatever it can get its powerful mandibles around.
OSRIC