The grapple arm is enormously useful, in my opinion. For one, it makes climbing much easier, and the lower caves are very vertical. It’s also possible to “Spider Man” around the entire region, which keeps you well away from many enemies. Used properly, it can also slingshot you, which allows the cumbersome Prawn suit to move at Seamoth-like speeds in bursts. As for those critters you do have to kill, a grapple arm allows you to attach yourself, then drill 'em to death. It’s boring and no fun, but it’s a practical solution to the psychopathic leviathans throughout the region.
I swear, I want a mod that lets me come back to this planet, scoop up my cuddlefish and some rabbit rays (and the sea emperors, I suppose) and then nuke the entire goddamn biosphere into non-existence. What a hellhole.