Do you know what a ChuChu is, small fry?
Pawprint Isle is one of the islands in the Great Sea in The Wind Waker. It is located one square east of Windfall Island on Link's map. The island is actually made up of five small plateaus coming out of the water, forming the shape of a pawprint. Unlike most islands, this small one has two different hidden places full of treasure. In the waters around this island is a Piece of Heart, found by using a Treasure Chart found in the Tower of the Gods.
First Hidden Cave
The most obvious of the underground caves is right in the middle of the island. On the main part of the island, the palm of the pawprint, is a large blue and white orb. The entrance is hidden behind grass. If Link crawls into the orb, he will drop underground into a cave full of ChuChus. If he defeats the ChuChus and explores a bit, he will eventually find a Joy Pendant, a purple Rupee, and a Piece of Heart.
Second Hidden Cave
The second cave on this island is a little harder to find, and cannot be accessed early in the game. Link must first have the Hookshot (found inside of the Wind Temple) to climb onto the parts of the island that look like the pawprint's fingers. If Link uses the Hookshot on the palm trees on these islands, it will lead him to another hidden cave. Inside that cave is a silver Rupee protected by Wizzrobes.