Here is the full list of all 18 Mermaid Land achievements.
Collect 20 stars
Win three levels
Remove 1000 animals
Earn 300 gold coins
Win the level with 5 saved moves
First start of the game
Remove 100 animals
Complete 10 tasks
Complete 15 levels
Match 5 figures 10 times
Earn 999 gold coins
Use booster Hummer 10 times
Use booster Bomb 10 times
Use booster Net 10 times
Use booster Lightning10 times
Buy extra moves to win
Win 5 levels on the last move
Buy 4 any boosters