SpongeBob SquarePants: Battle For Bikini Bottom - Rehydrated

Prawn is the boss that you encounter at the end of the level, the Mermalair. This fight is very similar to the Jellyfish King boss fight, but a little more elaborate and slightly longer. Run along the outer circle that has no lights on it, and jump over Prawn's sound wave attack when it gets close to you. After a beat, his shield should go down and on the floor with lights there will be a few pathways leading up to Prawn. (Pathways that are white, with no color are the safe ones.)

Use your bubble bowl ability to hit Prawn. After the first hit back up to the outer part of the platform. Some Ham-Mer robots will spawn in, just kill them as you repeat the previous process, hit Prawn when he's vulnerable a second time, and then repeat the process a third time. He'll attack more after each hit so just be aware of that.

After the third hit, a cutscene will play and the achievement will unlock.