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