Note: The Sonar Collections Dock becomes available to purchase after the mission The Merryweather Heist, Michael can buy it, but also Franklin. See Nuclear Waste for information on another collection mission based from this location which has the potential to completely cover the cost of the dock.
The player then needs to use the Dinghy anchored at the dock to look for the pieces. The boat is equipped with sonar that marks a circular green search radius on the map, to indicate the general area where the pieces are. Once the boat enters the vicinity the precise location of the piece is marked. The player needs to go to these locations and use a scuba suit to dive in the ocean and collect the pieces underwater. The middle of the search radius is always where the submarine piece is located. There may occasionally be more than one piece in the same vicinity.
Note: There is no need to collect a scuba suit beforehand, as the protagonist will be automatically fitted with the gear once he exits the Dinghy.
During these dives, the player may also find other items such as armor, health, and weapons. And if the location of underwater cash-filled suitcases is known, these can be picked up en route. However, the Nuclear Waste barrels will only spawn when using the minisub, so the player cannot "double up" the mission.
Sharks are a real danger when doing this mission as unlike the Nuclear Waste pick-ups the player must exit the safety of the boat to collect the sub pieces. Sharks appear as red enemy dots on the radar; if one is near a dive location, the player will need to leave the vicinity and return.
Collecting all the pieces will require the player to circumnavigate the entire island, with pieces located from Paleto Bay to the Los Santos docks. If playing as Michael and Trevor while their exile from Los Santos is still in effect, an additional danger comes from Martin Madrazo's men who will attack the characters on sight if they enter the city; unlike the sub, Michael and Trevor are fully exposed in the Dinghy and have to come close to shore to collect some of the pieces, making them subject to being shot at from the shore.
Any of the three protagonists can collect the pieces, but only Michael can return then to Abigail. The mission What Lies Beneath is unlocked once all 30 pieces are collected.
Unlike the Spaceship Parts and Letter Scraps, the Submarine Parts do not count towards 100% completion.
- The player 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 are near the location that will need to be explored to find Submarine Pieces.
- 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.
- The boat will be carried away from where you parked it. The distance it moves depends on water roughness.
- The player will encounter some sharks while looking for the pieces. If the shark its not provoked, there will be no problem. However, if one does get aggressive, it's possible to take it out. Target locking does not help in this situation. Sharks appear as a red dot on the radar. It's also possible to shoot sharks while standing in the boat. Crawl into the craft (don't jack it) so the weapon can be selected.
- Park the Dinghy smack dab in the middle of the focused search radius. A blue blip immediately becomes the Dinghy marker the moment the player dives out of the boat. The white expanding ring remains on the radar to help locate the piece while the player is swimming around.
- An internet article from Public Liberty Online after the mission Blitz Play mentions the Submarine Pieces, the article reports the death of Frank Mathers while he was testing a submarine, and that the submarine break apart spreading its pieces across the ocean.