In Splash we have three different types of chests:
A large round Bonus Chest - This chest may appear in your reef at times unlocked or locked - you can unlock this chest by watching a video, or using splashcash!
A gift chest - This is a gift from your buddies, and it will have their photo above so you can see who it is from.
A release chest - this is normally left behind when you release fish, it can open up to reveal stones, and other helpful ingredients to create more fish.
Some abilities will only work on certain types of chest.