Until about 50 years ago oceanographers were limited to doing work by "remote control." They had to use artificial hands (grabbers and samplers) and eyes (cameras) lowered from surface ships. Man was not present at the work site.
This was analogous to flying in a balloon over land on a dark night with no direct contact or observations possible. Grapple hooks were lowered, along with a camera or two, to photograph the scene below. Then the haphazard collection of physical samples and photographs would be studied and analyzed. Doing science this way on land would be laughable. Yet this was pretty much the way oceanographers worked from ship platforms at the outer skin of the sea.
Development of the self-contained underwater breathing apparatus (SCUBA) after World War II opened the shallow depths (to about 150 feet) to the oceanographer. For a modest investment, and a training course, the scientist now could work inside the sea. Thousands of oceanographers have learned how to use SCUBA as a tool of the trade.