JOHNSON-SEA-LINK I & II, Harbor Branch manned submersibles devoted primarilly to research in the marine sciences, are classed and certified to a maximum operating depth of 3,000 feet by the American Bureau of Shipping (ABS). The forward acrylic sphere is fine inches thick and provides panoramic visibility for a pilot and one observer. A second crew member and another observer occupy the after observation chamber where a video monitor and side view ports provide forward and side observation.

The evolution of specialized equipment such as manipulator arms, suction devices, and rotary plankton samplers has made it possible for crewmen to accomplish almost any work from within the subs that once was done only by divers. The JOHNSON-SEA-LINK submersibles are further outfitted with such state-of-the-art equipment as active sonar, laser aimed video cameras, and Harbor Branch-developed xenon arc lights. The arc lights approximate sunlight, illuminating underwater scenes in true color and near daylight conditions, even in the darkest seas.

These sophisticated and highly maneuverable free swimming submersibles have been in operation since 1971 and 1975. Maintained and operated by experienced and expert pilots and crews, they are further supported by in-house ocean engineers.

Typical applications include benthic and/or mid-water observations, photo/video documentation and collection of organisms; dump site inspections and monitoring; punch and box coring; search and recovery; bottom surveys; photogrammetric surveys; archaeological site documentation and recovery; and environmental impact studies.