A five-person dive team from CFB Esquimalt retrieved the mortar from the Cosens Bay area Friday morning.
The explosive, which was about 15-centimetres long with fins on it, was spotted by a resident who was on the water earlier this week.
The dive team's Lt. Mike St. Pierre told a news conference that the team transported the mortar to a military base and blew it up with explosives.
St. Pierre says the device was likely left behind from the Second World War, when military training took place around the area.
He says the team will do a further check of the Cosens Bay area to make sure there are no more military ordinances in the water. (CKIZ)