New Zealand and United States navy officers have honed their mine-clearing skills off Northland's coast during a two-week a multinational exercise.

Exercise Fulcrum, a training activity involving primarily the Royal New Zealand Navy (RNZN) and the United States Navy, tested divers and operators of autonomous underwater vehicles in very shallow water mine countermeasures in Bland Bay, Whangaruru, in the last two weeks of February.

The exercise involved dive ship HMNZS Manawanui in Bland Bay, and about 50 divers and specialists from the RNZN Littoral Warfare Unit's clearance dive group, the United States Navy's Explosive Ordnance Mobile Unit 5, divers from Britain, and autonomous underwater vehicle specialists from Australia and New Zealand, who were based at Bland Bay Motor Camp.

Diver Lieutenant Teina Hullena said Bland Bay was chosen because it was an ideal training area.


"We look for a good gradient, a good training environment," he said.

"It's the east coast, with good water - not as rough as the west coast."

Before the exercise, crew on Manawanui set 16 training mines in the bay to a depth of up to 30m, and they were differently shaped to challenge the autonomous underwater vehicle teams.

Crew onboard HMNZS Manawanui deploy a
Crew onboard HMNZS Manawanui deploy a "Manta" training mine in Bland Bay.

The vehicles travelled across the bay in a grid, sending back signals that displayed on a computer screen on shore. Vehicle operators identified mine-like objects and noted their position, allowing divers to investigate and neutralise them.

The exercise was a success, with all 16 mines located by the teams.

Mine recovery involved floating the mines to the surface using balloons - no mean feat considering some weighed up to half a tonne.

The teams were grateful for additional training with Whangarei's Northern Emergency Services Trust rescue helicopter, which practised lowering a swimmer to rescue divers and hoisting them on a winch to the shore.

Primary school pupils and teachers from Whangaruru School visited the campsite to see how the equipment worked and play sports games with the divers.

The Littoral Warfare Unit consists of component groups who handle mine countermeasures, diving operations, underwater surveying and underwater search and rescue.

Last year the unit's divers trained with the Americans in Guam in explosive ordinance disposal.