Once you have entered the flooded underground (see related question), you make your way left to find the Bone and the Key Ingredient. Climbing back up past the "millipede worm" will let you exit through the Ingredient room.
It is in the shark cave
on the roof of the ancient ruins
in the ancient ruins of shark tooth island
on top of the ancient ruins
deep in the ancient ruins
Go to the right from Main Street and you will see the sign "Ancient Ruins".
No. The "temple" is the ancient ruins to the right.
go to the ancient ruins and you will see a cave
It is a sandy, touristy island with ancient ruins and one very nasty shark.
The ruins are just to the right of the first village (Main Street) on Shark Tooth Island.
Go to the right from Main Street and you will see the sign "Ancient Ruins".
on top of the cave in the Ancient Ruins