The accident occurred outside the Birka terminal when two tug boats were towing the canal boat Diana. One of the tow boats, with the 37 year old man onboard, suddenly sank.
The fire service’s rescue divers found the man at a depth of 20 metres. He had been trapped in the ice cold water for more than 15 minutes and was taken to hospital with serious injuries.
The sunken tug boat was being salvaged on Saturday after it began leaking oil.
“Now the Maritime Safety Inspectorate will try to establish what happened,” said Henrik Ahlqvist, at Stockholm harbour, to TT.