Emeralds are an in-game currency in Paradise Cove. They can not be bought but can be acquired through quests and by sending ships on voyages.

Emeralds are used to upgrade emerald merchants. They are craftable after reaching level 25.

You can gain emeralds from

Ships Tier ? ?
Dark Cruiser
Cpt. Jim's Cruiser
Crafted Cruiser
Gail's Ark
The Magellan
Cpt. Richard's Battleship
Cpt. Robert's Galleon
The Emerald Queen
Barco del Muerto
Ghost Ship
Sea Beast
Snowy Battalion
Party Ship