You find shell bits in the central light area. Go up to top of hill and shoot down blue bird for blue coin. Then slide down trail of coins to get into hole. Can just bounce on it and float in.

Red coins on a floating sand bird. There are 7 red coins on his back. a blue one floats by in a cloud. Get out onto right wing and when he begins to turn sideways stand on the little block that sticks out. Now he flies to a tower where the 8th one is. Jump to get it and the shine appears right there.

Super Mario Sunshine Walkthrough