"Abigail" is a NPC in Grand Theft Auto V
Abigail is the second wife of the famous TV personality Frank Mathers. She explains that his submarine broke apart while he was trying to save the San Andreas White Shark. There have been rumors around her being involved in tampering. Specifically with the airlock. This hasn't been proven though.
She recruits Michael to help with the search for 30 Submarine Pieces.