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