Lurkers

Lurkers are tentacled creatures which infest the waters of underground lakes. They appear in Ultima Underworld I and II.

Description
Like the kraken of Britannia's seas, no full specimens of a lurker has been recovered, leaving much unknown about their anatomy. They are often seen with the top of their head peering just above the surface of the water, and are known to attack their prey a number of strong grasping tentacles.

Lurkers typically pose little danger to swimmers who are able to quickly disembark a given body of water, but can overwhelm adventurers who find themselves swimming out of reach of shore, particularly when the hunt in groups. Many lurkers are even bold enough to assault explorers at the edge of their waters, although those on land have little to fear from these beasts and may frequently be able pick them off at a safe distance using ranged weapons.

Deep Lurkers
In the deeper reaches of some underground systems, there lurks a larger, more aggressive variant of the lurker. Recognizable by their bright green coloration, these "Deep Lurkers" possess considerably more fortitude than their smaller cousins, and their bite is known to deliver a deadly venom.