The species was confirmed on Monday by experts studying a series of photos of the bird, which was seen by dozens of twitchers.
Birdlife Finland's rarities committee will decide whether to add the bird, also known as a Pacific Loon, to the list of species native to Finland. If so it would become the 463rd on the list.
The Pacific Diver breeds in Alaska, northern Canada and eastern Russia, but has also been seen elsewhere in North America and Asia as well as in recent years in Greenland, Britain and Spain.
