Volunteer divers have killed a record 47,000 crown-of-thorns starfish in seven days on the Great Barrier Reef.

Twenty-five volunteer divers have returned from a nine-day mission to cull the marine pest.

The divers operated in groups of 12 completing three dives of up to an hour each per day.

The injected the starfish with bile salt to kill them.

Authorities from Queensland Parks and Wildlife joined the expedition too, so they could survey the concentration and location of the of starfish hordes.

Some of the members of the team described mind-bending amounts of starfish, with animals stacking on top of each other to reach the coral on which they feed.

While the estimated tens of thousands killed on the trip may have put a dent in the population, it is by no means the end of the invasive species.

It is hoped that recent federal funding will help culling trips continue.