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.
The Royal New Zealand Navy is participating in the exercise and provided sonar capability.
The Disaster Victim Identification unit is also involved as well as the Harbour Master, Taupo Airport Authority, Coast Guard and Fire and Emergency NZ.
Police National Dive Squad head Senior Sergeant Bruce Adams said the exercise was a great opportunity to refresh members' skills and work with other agencies in a real life scenario.
"The public will have seen us in the area working to recover the two wrecks from the water."