Alvin is a Deep Submergence Vehicle (DSV), the first of its class, designed to explore the ocean floor for oceanography. Modern nuclear submarines, like the American Seawolf class, have a crush depth of 730 m (2400 ft), while Alvin has a crush depth of 4000 m (15,000 ft). Alvin was constructed at General Mills' Electronics Group and commissioned on June 5, 1964. Weighing in at 16 tons, Alvin is owned by the United States Navy and operated by the Woods Hole Oceanographic Institution (WHOI) in Woods Hole, Massachusetts. Throughout its 40-plus years of oceanography service, Alvin has received a complete overhaul on several occasions.

Alvin was built to replace bathyscaphes and other, less maneuverable oceanography vehicles. One of its primary structural materials is syntactic foam, a composite material consisting of glass microspheres embedded in a matrix of epoxy resin. Syntactic foam is buoyant, yet it can withstand extreme pressures. At its maximum depth, the pressure on Alvin is equivalent to 40 atmospheres.

Because so few vessels in its class have been built, Alvin can claim multiple unique accomplishments, both practical and scientific. On April 7, 1966, Alvin was employed to recover a 1.45-megaton hydrogen bomb lost during a US Air Force refueling accident known as the Palomares Hydrogen Bomb Incident. A mathematical technique, Bayesian search, was used to decide which areas of the ocean floor to search. The search took several weeks.

In 1977, Alvin achieved a major accomplishment in oceanography by locating black smokers, a type of hydrothermal vent, around the Galapagos Islands in the Pacific. Black smokers are notable because they harbor one of the only ecosystems on Earth entirely independent from the Sun's energy. Around black smokers, chemotrophic bacteria thrive from released chemicals, allowing the growth of animals that feed on them, like mussels, shrimp, and tube worms.

One of the most famous applications of Alvin in oceanography was its exploration of the RMS Titanic in 1986. The footage was broadcast on several TV documentaries. Many of the photos were also published by the National Geographic Society, a major sponsor of the expedition.