The Nautilus is a B.O.W. that appears in Resident Evil: Dead Aim. This creature was one of Umbrella's failed experiments and was believed to have been destroyed in the Umbrella Waste Disposal Facility in the Atlantic Ocean, but due to the mismanagement of the facility, the creature was allowed to grow and reproduced asexually in the waterways. Observations and data were collected on the strange mutation, but its origins remain uncertain. They were originally marine ascidiacea (more commonly known as ascidians or sea squirts).
Bruce McGivern and Fong Ling encounter two Nautilus inside the facility's waterways. The creatures are immobile and cannot harm directly, but they continuously spawn Torpedo Kids that seek out and home in on prey. The Nautilus can be killed relatively quickly with a shotgun.