The Great Booga Shark (or simply Booga) is a shark, whose species is unknown. Oddly enough, Booga has a collar. He has a massive fishhook through his fin that doesn't seem to hurt him and his tongue hangs out of his mouth like a dog. He may be a reference to the megalodon - a massive prehistoric shark. Booga is the villain of Shark Tooth Island.
As an aggressive shark, Booga is mean looking and outright strange. It takes on some characteristics of the dog, having a collar and its tongue hanging out of its mouth. The shark's character is not very detailed as there is not much screen time for it. Perhaps the character's purpose is to tell a story similar to Moby Dick.
The Booga shark is a huge shark in Booga Bay. He seems to be old, because it is said that he:
...used to be worshipped long ago and still prowls the waters today.
After you give Booga the Calming Potion, he will fall asleep. Giant green bubbles pop from the water from where he is sleeping and he does not wake up, making it safe for you to swim over the bay. You then swim over to Castaway Island, where you rescue Professor Hammerhead and and the lost boy. They will follow you back to the main island, where you will be rewarded the Island Medallion.