A B.O.W. born from early experiments with the T-Virus. Almost immediately upon beginning the virus research, a huge number of failed experiments were produced. The Lurker is one of those failed experiments, and it is made from an amphibian frog base.
Their eyes and ears have devolved greatly in this form, but their ability to sense prey has been evolved to an almost supernatural level. Their tongues in this form have become strong enough to actually impale a human target with little effort. Their digestive systems have also developed to the point where they can swallow a human whole, as those systems are now strong enough to kill whatever prey they swallow almost immediately.