There are two Johnson-Sea-Link submersibles, both built in the 1970’s to support underwater science and exploration. They were invented by Edwin Link, a famous engineer who also invented the Link Trainers used to train airplane pilots in World War II. Each Sea-Link carries four people. A pilot and a scientist ride in a 5” thick bubble of Plexiglas on the front of the sub. A second pilot and scientist ride in an aluminum compartment in the back, where they can communicate with the front chamber by headsets and look out through thick plastic windows on the sides. The submersible has an extensive suite of hydraulic tools for collecting specimens, instruments for measuring the conditions in the water, and cameras for recording what the scientists see.

The original Sea-Link submersibles were designed as “lock-out” subs. At depths as great as several hundred feet, the aft compartment could be pressurized, allowing divers to leave the sub and work outside, connected by tethers. Because most work is currently done at depths too great for lockout work, this capability is not longer available