Boaties on Lake Taupo may have noticed some activity involving members of the Police National Dive Squad.
The squad's annual training exercise has been taking place just off Five Mile Bay.
The exercise simulates the recovery operation following a collision between two aircraft over the water, with debris spread across a large area and at varying depths.
Two aircraft wrecks, a helicopter and a fixed-wing aircraft, were set up in Lake Taupo last week in order to create a realistic scenario.