Here is the full list of all 35 Curse of the Sea Rats achievements.
Beat Murat Reis.
Beat Krabawaki and The King Clapper.
Beat Fatso.
Beat LaChusa.
Beat The Lighthouse Keeper.
Beat Fatsie and Fatso.
Beat Rama Cinnamon and Banana.
Beat Freddy Eightfingers.
Beat Short Fuse Jones.
Beat Sharpie The Sharp.
Beat The Necromancer.
Gain Morrigan's favor.
Beat Flora Burn.
Beat all bosses.
You haven't even tried...
You are halfway there.
You almost made it!
You've made it!
Discover 100% of the map.
Open all doors.
Get all the collectibles.
Unlock full skilltree of all characters.
Achieve level 15.
Defeat one of each enemy.
Resurrect Smiley Sam
Use both spyglasses.
Recover all Amelio's hidden treasures.
Find the Leprechaun's gold.
Help Mariah to get a sea sponge.
Help Mallor Majory get his wife's portrait.
Help Landsman Rogers improve his soup.
Help Poker Sailor to defeat the crab.
Help Rick fulfill his dream.
Help Granny Malone knit a scarf.
Make the bagpipe ghost friends again.