The crab is located on a beach that is located behind Gertrude's house, in the northern area of the game's map.

If you don't know where Gertrude's house is, it is marked as an NPC interaction where you get the weapon mission to find the parts to build Bob (da goat). (It is currently marked in this screenshot with my player icon.)

On the right side of Gertrude's house, there is a path that leads down to a beach area, where you can also find an abandoned boat launch/dock with a lock pick box and some scraps.


When continuing downhill towards the beach, you will see in the distance some small rock towers.

approach them

crab

thank you for your time, hope this helps