When you pass the statue with the giant caterpillar, there will be a hole lined with thorns. Jump down to the bottom to find the bone. To climb back past the caterpillar, go behind him as he passes, quickly go up the statue, and jump up to the platform.
A bone, Carbonated Milk and something called the key ingredient.
The bone is in a tunnel deep in the underground ruins. You will find it when moving left from the door with symbols on it. (see related question)
The sleeping potion for the shark requires three ingredients (coconut milk, bone, key ingredient). Find them and take them to the medicine man (in the "tree" next to the ruins), who will mix them into a coconut for you to feed to the shark. (see related question)
In the Temple
You can't swim to the island while the shark is active. But you can get the ingredients to make a potion that will put him to sleep. Gather the three ingredients (coconut milk, bone, and key ingredient) and take them to the medicine man, who will mix the potion in a coconut to feed the shark. Wear a grass skirt and he will help you. (see related questions)
it is under the big tooth
The Key Ingriedient which you get when you get the bone but don't jump and wait for a moving piece and jump on it then go left and then you have it.
The ingredients on Shark Tooth Island are1) coconut milk (from the island vendor on Main Street)2) a dinosaur bone found in the old ruins3) the green "key ingredient" also in the ruins at the far left of the cavesYou also have to have a grass skirt to convince the native man to make the potion for you. He is found at the top of the "tree" next to the ruins..
Along with the coconut milk and the green Key Ingredient, the bone is used to make a sleeping potion for the giant shark (Booga) that menaces the island. Get a grass skirt from the bay before bringing the ingredients to the medicine man. (see related questions)
The green "key ingredient" on Shark Tooth Island is part of the potion to put the giant shark (Booga) to sleep. It is down in the underground ruins, along with another ingredient, the creature bone. Open the underground door and go left to find the bone and then the key ingredient. (You already have the third ingredient, which is coconut milk.) (see related question)
You have the medicine man mix a sleeping potion, using coconut milk, a creature bone, and a key ingredient. The bone and green ingredient are down in the underground ruins. Once you have it mixed, you fire it from the shark feeding Coconut Cannon at Booga bay. (see related questions)
You need the three ingredients : the coconut milk, the creature bone, and the key ingredient. He will mix them into a sleeping potion for the shark (wear a grass skirt for him). The bone and key ingredient are underground in the ruins. (see related question)