With Carl Hubbs, he discovered the striped yellow butterfly fish that served as the logo of Birch Aquarium.

He joined the scientific staff of the Chief of Naval Operations, where he was the Oceanographer of the Navy from 1970 to 1984, and was the Senior Scientist at Science Applications International Corporation from 1985 to 1998.

[2] He wrote his 1955 Doctor of Philosophy thesis on A serological approach to the systematics of the viviparous sea-perches, family Embiotocidae under the supervision of Carl Hubbs at the Scripps Institution of Oceanography.

During a dive to 100 feet (30 m) off Guadalupe Island, Mexico, Rechnitzer speared a new species of striped yellow butterfly fish, which was subsequently adopted for use on the logo of Birch Aquarium.

[5][6][7] After graduating from Scripps, Rechnitzer became the Deep Submergence Research Program Coordinator and Oceanographer at the Naval Electronics Laboratory in San Diego.

He was the scientist in charge of Project Nekton in 1960, during which the Triete entered the Challenger Deep, the deepest surveyed point in the world's oceans, and dived to 35,800 feet (10,900 m).

In 1974, he was the US Navy representative on the National Geographic and Duke University expedition to determine the location of the wreck of the USS Monitor, an American Civil War-era ironclad warship.