A FAMILY got more than what they bargained for at Fingal Head Beach on Sunday. 

The family discovered a live military device, which had to be detonated by Military ordinates officers from Brisbane.

A 400 metre exclusion zone was created by emergency services, no person injured or property damaged.

NSW Police said the device was a marine marker which are used by the Military to locate vessels in the sea.

The devices are dangerous if they have not fully detonated.

The marine markers have a warning message on the side of the device not to touch the device and call police.