Hidden Golden Watermelon can be found on Beach Volley, the third world in Angry Birds Rio.
Send a bird off the right side of the level. After an explosion, a labeled crate will fall on a swing. Shoot the chain to get the box to fall and break.
Aim at the TNT in front of the slingshot. The melon will bouce around and eventually break.
This one is in side a labeled box in the middle.
This one is in a tree. It's dark green with a label on it. Once you hit it, the real melon should go flying and break.
This one's a little tough, it's high up in a labeled box. Use the white bird and aim as high as possible and drop the bomb at the top.
This one is labeled in the bottom-right square of sand use bombs to get it.
This one is in the tuft of grass below the slingshot.
There’s a labeled box in the bottom right of the level. Knock the stones over to hit the TNT box.
There is a labeled box in the bottom right. Take out the front of the level with Blu & Jewel. Use the Black Bird to take out the rest of the level, then use the White Bird to bomb the box.
You can see a label in the second patch of grass. The melon is the trough across from the beach balls. Aim at the suspended sand in front. This will take out alot and make the melon appear.
This one is in a labeled box just to the right of the middle valley.
This one is at the top-left in a patch of grass.
This one is in a labeled box directly beneath the slingshot. Use Blue & Jewel to go out and come straight back.
In a labeled box in the third of the string of umbrellas.
In a labeled box in the far bottom right of the level.