Turtle (DSV-3) is a 16-ton, manned deep-ocean research submersible owned by the United States Navy. It is sister to Alvin (DSV-2), and also an Alvin class Deep Submergence Vehicle. The Turtle was retired from active service in 1998. It now resides at the Mystic Aquarium in Mystic, Connecticut
The Turtle was designed to dive to 8000 feet. It has a hatch 2-feet thick, and held in place by the pressure of the water above it (it is tapered, narrower inward). The Alvin-class DSV were designed to replace older DSV, such as the less maneuverable Trieste-class bathyscaphes.