Emergency services were quickly on the scene and locals from the island of Marö assisted with the rescue. Two men and a woman were retrieved from the bracing waters and treated for shock.
"Three people ended up in the water and the boat sank," Stefan Johansson of the rescue services told the TT news agency.
A member of the coastguard services paid tribute to the quick-thinking locals who sped to the scene in their own boats to help, describing them as "heroes".
The three rescued individuals were brought onto the island of Marö where they were given dry clothes and treated for shock. They were taken to hospital for further treatment.
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The incident temporarily delayed the cruise ship which was heading to Åbo via Mariehamm but it resumed its course shortly after the drama.
"We are of course very glad that these people survived. They really had guardian angels with them," Helena Kneck, communications officer for Viking Line Sweden, told TT on Saturday.