A scuba diving instructor was leading a group of divers on Snapper Reef off the Cayman Islands on Monday when he spotted a nurse shark lying in the sand, as that particular species of shark is accustomed to doing.

But there was something unusual about the shark.

"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," instructor Brett Johnson told the Cayman Compass. Video footage shows what Johnson did next:

Johnson, 30, of Reef Divers calmly swam down to the shark and pulled a kitchen knife from its head.

"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 told the Cayman Compass.

"It was seen again on Wednesday swimming around the same reef."

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Still, the incident was a disturbing one. Sharks have been protected in the Cayman Islands since 2015, but apparently some haven't gotten the message.

"Sharks are an important part of the ecosystem and there is no reason to kill them," Johnson said.

"It would be great if all public docks and boat launches had signs posted on them reminding the public that it is illegal to take sharks from Cayman waters.”

"It's sad to see things like this happen," Johnson wrote on Facebook.

h/t SportDiver