A scuba instructor in the Cayman Islands has seen many hammerhead sharks in his years, but until recently had never seen a knife-head shark.
Instructor Brett Johnson was leading a diving class around a reef when he spotted a shark that didn't quite look right. He swam closer and noticed that the three-foot nurse shark had a 12-inch steak knife stuck in its head. Johnson, who took video of the encounter, thought the shark had swum up to him as if to ask for help, so he reached down and gently pulled the knife out. The shark swam away with a hole in its head, but Johnson said that he saw the same shark days later and it appeared to be doing well. (Cayman 27 TV)