Here is the full list of all 32 Another Crab's Treasure achievements.
Shoot a crab with a gun.
Get your shell back.
Try on every shell in the game.
Defeated Firth.
Learn all adaptations.
Defeated the Curdled Carbonara Connoisseur.
Defeated Praya Dubia.
Defeated Camtscha (For real.)
Defeated Camtscha.
Find a certain hero's helmet.
Fully upgrade Kril's fork.
Defeated Inkerton.
Defeated Petroch.
Defeated Roland.
Defeated Voltai.
Defeated the Royal Shellsplitter.
Unlock all skills on the Path of The Hermit.
Defeated the Ceviche Sisters.
Unlock all skills on the Path of The True Crab.
Defeated the Scuttling Sludge Steamroller.
Unlock all skills on the Path of The Predator.
Defeated the Consortium.
Defeated Topoda.
Defeated Heikea.
Defeated the Diseased Lichenthrope.
Defeated Pagurus.
Start the treasure hunt.
Purchase some insurance.
Fall off a cliff.
Defeated Magista.
Defeated a miniboss.
Defeated Nephro.