A German wartime mine netted by a fishing boat crew off the south Wales coast has been blown up.
A one-mile exclusion zone was imposed before the explosion
Bomb disposal experts imposed a one-mile exclusion zone around the 1,800kg (4,000lbs) device, considered a danger to shipping.
The deep water blast could be heard across Swansea Bay.
Fisherman Philip Wisby, who found the mine on Friday evening, said: "Once it's in the net you just close your eyes and head for safer water."
His vessel, Girl Eileen 2, was a mile off the shore between Mumbles and Swansea Docks when it caught the mine in its nets.
It was too dangerous to detonate the mine in darkness, but a dive team from the Naval Ordnance team from Plymouth did plant explosives on it.
The mine was designed to settle on the seabed and detonate when a ship passed through its magnetic field.
Petty Officer Sid Lawrence said the mine, one of the biggest the team had seen, "would cause quite substantial damage to a vessel if it was passing overhead".
He added: "They are designed to cause a massive bubble of air, as that hits the bottom of the ship it breaks the back of the ship."
It is thought the mine, measuring 12ftx3ft (3.6m by 0.9m) was one of the biggest and most destructive manufactured by Nazi Germany.
It would have been dropped into the sea by parachute during a Luftwaffe raid on Swansea, which was a target due to its port and nearby steelworks.