Sharkfood Island is a mysterious piece of land located out to sea at Treasure Trove Cove in Banjo-Kazooie.
At first, it is only a small mound and can't protect Banjo from Snacker the Shark (which it's named after). However, if a cheat code is entered correctly at the Sandcastle, the island will rise to reveal an opening. Once inside, the Bear and Bird can climb up the giant tree trunk in the middle to find a Stop 'n' Swop egg at the top.
There is a sign placed on top saying "Sharkfood Island".
Sharkfood Island before risen
The cheat code is "CHEATOUTOFTHESEAITRISESTOREVEALMORESECRETPRIZES".