Ultrafreeze, also known as El Frio, is a 61-meter (200-foot) former cargo ship and tugboat that was deliberately sunk to create an artificial reef off the Caribbean coast. The wreck rests about 30 meters (100 feet) below the surface and gets its name from the noticeably cooler waters divers encounter as they approach it.

In 1978, the former cargo ship caught fire while docked at Isla Mujeres and was damaged beyond repair. The following year, in 1979, authorities towed El Frio 7 miles (11 kilometers) out into open seas for its intentional sinking, thus creating an artificial reef and dive site. The wreck is now located just shy of the deep ocean drop-off, attracting larger marine life.

Hurricane Andrew split the hull in 1992, exposing the interior and creating a 90-degree angle. Both sections remain upright, providing access to various entry points and features such as a staircase, open cargo holds and loose cables. The coral growth is largely undamaged despite the hurricane's impact, making it an excellent dive site for advanced divers and those interested in exploring wrecks.