Where can you find a bottle for the potion on shark tooth island?

Answer 1

You don't use a bottle. In this early island, all you need to do is collect the 3 ingredients and take them to the medicine man at the top of the vine just to the right of the ruins.

The general process is

1. Get the coconut milk from the vendor on Main Street

2. A the ruins, push the big block right, climb the vine, and jump left onto the roof.

3. Get the translation page there, and open the face door in the underground by pressing the teeth that spell OPEN (and the nose)

4. Go left and get the bone from the pit, climb the statue, and go left again to get the Key Ingredient.

5. Get a grass skirt from the beach on Booga Bay, then climb the vine and give the medicine man the ingredients, which he mixes into a coconut.

6. Use the coconut cannon to feed the potion to the shark, and rescue the boy from the island in the bay.