A thoughtful scuba diving instructor proved that dive guides are good for way more than just navigation, as he removed a knife from a nurse shark's head off Cayman Brac.

Anyone who's spent significant time diving in the Caribbean, western Atlantic or eastern Pacific can appreciate the nurse shark – Ginglymostoma cirratum — which can grow up to 10 feet and is typically seen resting under ledges or on the hunt for crustaceans. Brett Johnson, a PADI Master Scuba Diver Trainer at Reef Divers, recognized one in need. You can see him in the video above removing a kitchen knife from the head of a free-swimming nurse shark.

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“At first it looked like it was just sleeping as most nurse sharks usually are, but then we noticed something coming out of its head," Johnson told the Cayman Compass. “I can’t say what happened or why it ended up getting knifed in the head, but fortunately it came out easy enough and the shark seems to be doing all right."

Johnson said that the same shark was seen swimming on the reef later that week.