Instructions
Paddle to the island with the tree stump. Sniff the stump to memorize the scent of hippo food.
Swim back to the stretch of beach that slopes toward Treely Woods. Sniff around the corner formed by the beach wall until you find the hippo food. The food will automatically be added to your inventory.
Return to the island with the tree stump. Circle closely around the stump until you get a prompt telling you how to put the food onto the stump. On a Wii controller, push "A" to set down the food. On a PlayStation 2 controller, push the square button to set down the food. The hippo will move over to eat, and you can jump on his back and from there to the next island.