The Crocodile Skull is treasure that can be obtained in the game Sly Cooper: Age of Thieves in the episode Coopers of the Caribbean. It is worth 211 coins and the time needed to get to the safehouse in time is forty seconds.
"Despite its scary appearance, this crocodile skull makes for a fancy alarm clock thanks to the clock in its jaws. No one knows how or why the alarm clock is even there. However, the fact remains that this clock is quite valuable, what with its gold color and all."
It is located underneath the harbor, where the Emerald Eclipse is located. Only Penelope has access to this treasure.