Guys, OP said 80s or early 90s. That's seaQuest DSV territory, ran from '93 to '96. Had the talking dolphin, underwater base, the whole shebang. Theme music had those synths u mentioned, OP. Almost positive that's gotta be it.

Hey, I collect rare VHS tapes, including broadcasts that never made it to mainstream release. No 'Journey to the Unknown' in my collection, but I do have contacts who delve in the greyer areas of film collecting. PM me with more details and I might be able to ask around.