Experts said the fate of the AN-28 civilian aircraft would have been far worse were it not for the marsh, which absorbed some of the impact and stopped the plane's fuel tanks from catching fire.
Rescuers flown by helicopter to the scene worked in waist-high freezing water to reach those inside the wrecked fuselage.
Jaan Alas, 49, died in the accident, while the two people in a coma were the plane's 23-year-old pilot and a 10-year-old boy, said Interior Ministry spokeswoman Anu Adra.
Five of the victims were taken to a Tallinn hospital and nine to the island's own hospital in the town of Kardla.
Others made it on foot to the village of Palade, a kilometer away, where they warmed up with hot drinks and fresh clothes.
Two more helicopters and a plane later joined the operation.
John Pass, 38, a Canadian businessman living on Hiiumaa who was on board the plane, told The Baltic Times that after helping the boy and an old lady from the waterlogged cabin he put the boy's broken leg in a splint before carrying him to safety.
"I take that plane every week, and it's always rather shaky during take off and landing," said Pass, who has been living in Estonia for eight years.
"When it crashed, it went down very quickly, and at first I thought we had fallen to the sea as water started to come from the broken windows. But then I saw trees."
He said the passengers got out of the plane calmly, helping each other. The rescue team arrived after half an hour.
"I've spoken many times with the boy's father. I'm going to visit him in the next few days," said Pass.
The stricken aircraft, which belonged to the Enimex company, was contracted by ELK (Eesti Lennukompanii) to run the regular half-hour service between Tallinn and Kardla on Hiiumaa.
In a preliminary report on Nov. 24, a special commission under the Transport and Communications Ministry cited several possible causes for the accident, including human error.
The Estonian Civil Aviation Administration is due to debrief the crew over the coming week and is now studying the plane's black-box flight recorders.
The flying licenses of the six AN-28s registered in Estonia have been suspended until noon on Nov. 26.Kuldar Vaarsi, spokesman for the Transport and Communications Ministry, reported that the AN-28 was built in Poland in 1986 of Russian design. The AN-28 is considered to be a reliable light aircraft.
One cause of the crash may have been differences in wind speed near the ground and hundreds of meters up in the air, said Rein Porro, dean of Estonia's Aviation College. He told theEesti Paevaleht newspaper, "By catching an air pocket, the plane loses lift for a while and might fall before the normal situation can be restored."
Porro, who has personal experience of flying AN-28 planes, doubted claims by other experts that ice might be the cause.
"The AN-28 has an excellent anti-icing system, which keeps working in frosts below minus 20 degrees," he said.