Lurker

The Lurker was one of the first bio-weapons created from James Marcus' early experiments with the t-virus along with the Eliminators and Plague Crawlers. It was an amphibian that had grown to large proportions. Its eyes had devolved greatly from the mutation, but this was compensated with improved hearing senses and a strong body that was almost impervious to bullets, yet significantly weak to knifing attacks. They attacked with sharp piercing tongues that could actually impale a human target with little effort and could swallow a human body whole due to their developed digestive system.

However the mutation showed no increase in intelligence and research on them was abandoned, since their most notable trait - randomly attacking all moving objects - was of little interest to the advance of B.O.W.s. They were also very easily scared off and a single bullet was all that was needed to drive them back into the water. Some of these B.O.W.s escaped and were spotted at the sewers during the Raccoon city incident.

Research on Frog-based B.O.W.s would later continue on in the form of the MA-124 Hunter γ, with similarly disastrous results.

Resident Evil: The Deck Building Game
The Lurker is an Infected card in the Resident Evil DBG expansion Alliance. Its health and damage are 10 and its decorations given are 1. This makes it the weakest Infect in the entire game alongside the Bui Kichwa. This seems quite odd, seeing as how Lurkers are capable of killing the player almost instantly in RE0. They have no special effects.