Lieutenant JG Tim O'Neill was the communications officer of the seaQuest DSV 4600, originally serving under Captain Marilyn Stark. He remained aboard the boat after she had been relieved of duty and the seaQuest was refitted to serve as more of a research vessel. O'Neill specialized in foreign languages, was fluent in at least a dozen and could adequately speak several others. He also shared some sort of unknown psychic link with Darwin which allowed him to sense when Darwin was ill.