Patricia Sawyer

 was a marine biologist.

She thought she was hallucinating when she saw the Fourth Doctor, Romana I and K9 Mark II exit the TARDIS. She didn't believe that the quids couldn't communicate using symbolic logic. She swam with the Doctor to a sunken submarine and was surprised to see an air pocket. She could see sea goblins outside the ship. (AUDIO: Phantoms of the Deep)