A bomb squad was rushed from Christchurch to Port Chalmers on Sunday afternoon after a fishing boat dragged up what appeared to be an explosive device from the ocean floor.
Police say the device looked like a mortar and part of it appeared to be in good order.
The vessel was moored in Careys Bay for on Sunday afternoon and the immediate area was cordoned off by police.
Later, the device was discovered to be a practice bomb of unknown vintage.
It contained no explosive charge and the cordon was lifted.
The device was about 50cm long and weighed about 10kg.
