To get the Sea Shrimp Fighting Arm Fragment in the Deep Sea Trek game, first equip the compass with our escape pod #5 as the starting point. Set off in the south-southwest direction which is the direction to Green Island.

1. Successfully reach Green Island without going ashore. Then dive down to the bottom of Green Island, the floaters fix the middle of the island.

2. Dive along this bearing until you see the bottom of the sea. Once you reach the bottom of the sea adjust your orientation to the middle of the south-southwest.

3. Then keep going straight along the bottom of the sea. A short distance away we will find a relatively small wreck.

4. Inside and outside this wreckage are tons of fighting arm pieces, as well as power drill arm pieces. The ones that don't have the power drill unlocked can be unlocked here as well.