Cayman Sound is an island in Assassin's Creed IV Black Flag
The Cayman Sound is an island in the game Assassin's Creed IV: Black Flag. It is right next to the Grand Cayman, just being on the other side of the hilly region. There are several things you can do there, especially if you are doing the Templar hunt for the five keys. You will find an assassin there named Opia Apito, a lady from the Taino origins. She will challenge you to a hunting contest, where whoever hunts the most hutias win. However, if you come across a white jaguar and kill it, you will win instantly. Opia will then help you, where you do missions that include taking down a frigate, exploring a new island, and of course, killing someone to get a key. Other than the Templar hunt, it is good to find hutias if you need some of their pelt. There is also a viewpoint which you can sync to find more things, and there is a treasure map you can take.
Assassin's Creed IV: Pinos Isle Treasure Map (leads here)