Submarine Piece collection is activated by speaking with the random character, Abigail, who stands on the left side of the Sonar Collections Dock. She asks if you were a fan of Frank Mathers, and indeed you are. He's a TV personality that switched his passion from space to undersea exploration. Well, Abigail was his second wife. Frank is dead now and she is penniless. It is rumored that she may have had to do something with his passing.
Abigail explains that his submarine broke apart while trying to save the San Andreas White Shark. His body was never found. When asked about the story of the lampered airlock, Abigail quickly squelches, "That was never proven." She wants your help to prove that Frank is dead and the airlock was responsible, so she can collect the life insurance. She makes a promise to make it worth your while. Abigail becomes a new contact.
A Dinghy is located in front of the Submersible at the right end of the pier and is used to search for the 30 missing Submarine Pieces. Searching for Submarine Pieces is a lot like searching for Nuclear Waste in the submarine. The Dinghy has an onboard sonar that works similar to the Trackify app. It's used to hone in on the location of a collectible, and it only tracks one piece at a time.
After the player (as Michael, Franklin and/or Trevor) has collected all 30 pieces, Abigail will appear at the Sonar Collections pier again, paying Michael all of ten dollars for his trouble and denying his observation that the airlocks had indeed been tampered with. She then leaves, claiming (certainly falsely) that she will report the matter to the FIB. Michael can choose to kill her or let her go; either way the mission is passed.
- Unlocked after "The Merryweather Heist": Abigail appears on the Sonar Collections Dock after "The Merryweather Heist" is completed and after the the Sonar Collections Dock is purchased ($250,000).
- Weapons, armor, health and hidden briefcases: You only receive $10 for collecting all the Submarine Pieces; however, there are many treasures underwater that can make this well worth your while. Keep your eyes out for high concentrations of weapons, armor, health kits and hidden packages (briefcases of random amounts of money) around the same ship and plane wrecks that you'll be exploring to find Submarine Pieces. You can't find such high concentrations of weapon drops like this on land.
- Sonar tracking tip: The Dinghy's sonar places a circular, green search radius on the map. Open the map and place a destination marker in the middle of the green search circle. The middle of the circle is always where the underwater Submarine Piece is located. Note: while the green search circles only appear while in the dinghy, the white sonar rings and audible pings occur whenever the current player character (not just Michael) is nearby, whether swimming, in another watercraft, or even driving by on land if the piece is close inshore.
- Scuba gear and diving: As soon as you jump of the Dinghy, you're automatically fitted with scuba gear (no need to suit up beforehand). To dive beneath the surface of the water, simply press the RB (Xbox 360) or R1 button (PS3). To get back in the boat, approach it and press the Carjack button (Y on Xbox 360 or Triangle on PS3). The boat will be carried away from where you parked it. The distance it moves depends on water roughness.
- Shark: You encounter all sorts of sea life on your journey, including sharks. If you don't provoke a shark, you will be just fine - enjoy their beauty. However, if one does get aggresive, you can take it out. Target locking does not help in this situation. Sharks appear as a red dot on the radar. You can also shoot sharks while standing in the boat. Crawl into the craft (don't jack it) so you can select your weapons.
- Dinghy marker: Park the Dinghy smack dab in the middle of the focused search radius. A blue blip immediately becomes the Dinghy marker the moment you dive out of the boat. The white expanding ring remains on your radar to help located the piece while you are swimming around.