Big school of Hammerhead sharks in Cocos Island, Costa Rica. This is my best picture of a school of Hammerhead sharks in more than 11 years of diving/working, more than 9000 hours of diving. There is not a better image from a school of sharks coming from front and with out bubbles. I took this image in 2008 where you can still see large numbers of sharks; unfortunately sharks populations have decaying more than 90% world wide so you don't see this today.