Continue left and get the Key Ingredient and leave the underground ruins. The bone, Key Ingredient, and coconut milk go to the Medicine Man in his bamboo "tree house" that somehow drops coconuts. First get a grass skirt to wear (so you fit in), then push the block over and climb the vine to have him mix your three items into a sleeping potion. Take the coconut to the cannon and fire it into the water, and soon the shark will be sleeping with the fishes.
first you have to go in the sharks mouth building. then you go through the maze(underground) and the bone is at the end
You get the translation paper and go to the cave its on the top left of the cave.
There are no mermaids in Shark Tooth island, you do go into the ocean
In Poptropica, after you finish Shark Tooth Island, you can go to Time Tangled Island and go through such a fiasco!
you go to poptropica shark tooth island then you go to the person with the shark fin and then click on him....and then you will have the shark fin.
You have to go into the ancient ruins and then get past the secret code door. The bone is at the bottom of the area with spikes on either side, just past the giant shark statue with the giant catapillar.
Climb back up past the worm statue, go left to find the chamber with the final (key) ingredient,
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 go to shark tooth island then you try to dodge the shark attacks
You can go to another island and complete it. When you get a medallion you have completed that island :)
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.
thats easy, but its hard to explain with words. go to youtube and type in poptropica shark tooth island walkthrough.