Emergency crews desperately searching for four people feared dead after a military helicopter crashed off Hamilton Island.
The military helicopter, known as Taipan, had been engaged in a two-helicopter mission when it crashed at about 10.30pm on Friday.
There were four Australian crew aboard the MRH-90 Taipan aircraft at the time.
The second chopper immediately began a search and rescue operation.
An exclusion zone spanning 1000m has been established where a debris field was found.
The retrieval operation will focus on a site in the middle of the Whitsunday Passage between North and South Molle Islands.
Since the Howard Government purchased the fleet of 47 helicopters Taipan in 2004 and 2006, they have been grounded several times and involved in multiple crashes.
The most recent crash happened just four months ago during a night-time counter-terrorism training exercise on March 22.