The Mermaid Statue is a randomly placed destructible item that exists in the Sea of Thieves. They were originally introduced to the game during The Sunken Curse pre-event for the Cursed Sails DLC. The statues could be found in the deeper waters of the sea and destroying them would reward the player with Doubloons, an in-game currency that could be spent with Duke, a member of the Bilge Rats.
In the Shrouded Spoils DLC, the statues make a return, and this time they reward the player with gems that can be carried on ships, stolen by pirates, and given to the Gold Hoarders faction for reputation and gold. Handing in gems will count towards a shrouded spoils commendation so the statues will remain in the game as a permanent feature.
They can also damage the pirates to some degree if they are close. Using a cutlass at arms length just inside the aggro radius will help negate this. Players can use other weapons, like cannons and gunpowder barrels to damage and break the statues.
There are three colours: red, green and blue. Red is the hardest to break and blue is the easiest. The gems dropped will be the same as the colour of the statue. Blue gems sell for 1,000 gold, green gems sell for 1,500 gold, and red gems sell for 2,000 gold. The Bilge Rats reward you with commendations for selling 10 of each color.