He was about 45, said police and rescue-team sources.
Sources said the accident took place when the diver along with a partner went to a depth of about 30 meters.
Coast Guard and emergency rescue boats and Border Guard helicopters rushed to the spot, recovered the victim and took him to the hospital in a critical condition.
He succumbed to his wounds immediate after the incident, said the sources.
The divers were experienced and had the appropriate equipment, said police and rescue members.
Police are investigating to find out the reason behind the accident.
Earlier, on March 29, a middle-aged man was killed in Kuortane in South Ostrobothnia during training on diving at a quarry.
