From RWP Wiki
Hammerhead Beach is an old name for Treasure Trove Cove, a world in Banjo-Kazooie. In the past, it has been believed this was a separate new level; however it is simply the name used in some beta builds of the game for Treasure Trove Cove.
This world originally had an extended pier and giant beehives, among other things. These changes were removed and are no longer in the final version of the game.