A plaque in memory of a missing diver has vanished from the sea floor at the popular Poor Knights diving spot north of Whangarei.
John Barrie Cotton, 26, was diving with friends at a reef near the Northern Arch in 1979, when he failed to resurface.
A few months later, friends placed a bronze plaque on the ocean floor in his memory.
Dive Tutukaka director Jereon Jongejans said the missing plaque was a reminder to be cautious when diving in deeper waters.
Mr Jongejans says its disappearance is disconcerting as the plaque is much too heavy to have just washed away.
The plaque is presumed to have been stolen and melted down for profit.