One World War II mine has been made safe off the Whangaparaoa Peninsula and the Royal New Zealand Navy will be checking three more in coming weeks.
Practice scenarios became a little more real during the multi-national mine counter measures exercise held off the peninsula when Amercian, Australian and Japanese dive teams stumbled over the explosive relics.
The L Mark 1 Controlled Buoyant Mines were laid in the Whangaparaoa Passage between the peninsula and Tiri Tiri Matangi Island in September 1942.
Seven loops of 16 mines and two guard loops were laid over a fortnight at the start of a defensive mine laying operation which saw 1391 friendly mines laid in 10 harbours across the country.
The controlled mines would have been exploded from navy bunkers at the end of the peninsula if enemy ships were spotted in the Whangaparaoa Channel, Lieutenant Commander Trevor Leslie says.
"At the moment we have dealt with one of them, which has been made safe.
"We are going to be diving on the other three in the next few weeks to check their state because we haven't actually done detailed analysis dives on those yet," he says.
The navy says that because of their age and condition any remaining World War II mines are unlikely to be dangerous.
As a result the mines will be left where they are sitting on the seabed.
But staff recommend caution if divers come across a mine.
Any mine discovery should be reported to the harbourmaster or the Royal New Zealand Navy.
- Rodney Times
Are our classrooms becoming overcrowded?