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