Here is the full list of all 51 Coral Island achievements.
Complete artifact collection
Reach level 10 mastery in everything
Earn 10000k coins
Cook 15 recipes
Restore the temple
Complete sea critter collection
Reach heart 5 with 25 NPCs
Complete dinosaur collection
Ship a golden animal product
Reach heart 8 with an NPC
Purchase 10 clothing items
Complete gem collection
Ship all crops
Earn 1000k coins
Ship one crop 1000 times
Ship 5 animal products
Earn 500k coins
Heal all the sick coral
Earn 250k coins
Clear all the mine gates
Slay 20 enemy types
Reach heart 5 with an NPC
Ship 30 different crops
Give a gift to 25 NPCs
Earn 100k coins
Ship 2 animal products
Earn 50k coins
Slay 10 enemy types
Craft 15 things
Gain access to Giants’ Village
Gain access to Merfolk Kingdom
Earn 20k coins
Harvest 100 crops
Complete bug collection
Complete fish collection
Complete museum collection
Reach heart 10 with an NPC
Reach heart 8 with 25 NPCs
Reach heart 8 with All NPCs
Give a gift to all NPCs
Start dating an NPC
Get married
Have 2 children
Cook all recipes
Craft all things
Purchase 50 clothing items
Purchase all clothing items
Slay all enemy types
Ship all animal products
Ship everything in the game
Ship one animal product 1000 times