Due to explode at around 12.30pm, the Navy called for the fuse to be lit early at 12.05pm.
Measuring one metre long with a 45cm diameter, the suspected World War Two anti-submarine depth charge was found by a local group of recreational divers on Wednesday.
Located near the QEII Marina, a 200m exclusion zone was imposed around the largest explosive found in over three years.
'It was awesome, actually,' harbourmaster Captain David Barker said.
'This is the largest I've seen in almost three years, we have had some shells discovered but this is a reasonably large detonation.
'The Navy light a long fuse which has about five minutes of delay until it goes off. We then saw them all move out of the area. When it went off I could feel it in my feet, before the plume came up.'
Once detonated a large black column was seen, likely made of rust, sand and silt impurities as the charge was covered in marine growth.
'There was a larger plume of water then a black column within it, which is usually a good sign and means the ordnance has gone off as well as their explosives.'
Mat Le Maitre with a group of divers found the charge on Wednesday.
'They found it while out on a recreational dive and reported it to us on Thursday.'
Communications were made to the Portsmouth Royal Navy base.
'We have a standing arrangement to call for available aid to the civil authorities. Then they assess when they can send in a response team. In this case they were able to respond very quickly.'
Roughly a dozen mine clearance divers assessed the charge on Sunday on a reconnaissance dive to put a marker buoy on it.
Guernsey vessels Sarnia and Leopardess supported the Navy, while staff from Guernsey Coastguard and Bailiwick Law Enforcement assisted from the ground.
Critical worker exemptions were made to the divers with social distancing imposed to protect all parties from Covid-19.
Portsmouth Royal Navy are preparing a statement on the detonation.