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.
Defeated Praya Dubia.
Defeated Camtscha (For real.)
Defeated Camtscha.
Fully upgrade Kril's fork.
Find a certain hero's helmet.
Defeated Inkerton.
Learn all adaptations.
Defeated Petroch.
Defeated Roland.
Defeated Voltai.
Unlock all skills on the Path of The Hermit.
Unlock all skills on the Path of The True Crab.
Defeated the Ceviche Sisters.
Unlock all skills on the Path of The Predator.
Defeated Pagurus.
Defeated the Consortium.
Defeated the Scuttling Sludge Steamroller.
Defeated Topoda.
Defeated Heikea.
Defeated the Curdled Carbonara Connoisseur.
Defeated the Diseased Lichenthrope.
Purchase some insurance.
Start the treasure hunt.
Defeated the Royal Shellsplitter.
Defeated Magista.
Defeated a miniboss.
Fall off a cliff.
Defeated Nephro.