Here is the full list of all 20 Nelly Cootalot: The Fowl Fleet achievements.
Recruit an unexpected crewmember
Take an interest in Gloomholm's deceased citizens
Fulfil an ancient prophecy
Interview the head Ptarmigan's supporter
Track down Widebeard's Fowl Fleet
When two seashells come together
Wrap your ears around all of Spry's groove
Trounce Moses Melly first time around
Join the Merchant Navy
Meet the denizens of the Toff Races
Escape the MS Undeliverable
Make sure everyone's a winner
Make the lookout see a harmless tug boat
Catalogue all the stolen goods
Keep your eyes peeled in Chinatown
Become an aromatic master manipulator
Don't forget to return what you borrow
Shoot down all the varmints on your first attempt
Find out what Sebastian thinks about 20 characters
Unlock all achievements in Nelly Cootalot: The Fowl Fleet