Theory: Gas bubbles coming up from cracks in the lake bottom.
Objection: Some sightings may have been misinterpreted, but it is difficult to imagine gas bubbles that can be followed across the lake.
Theory: A row of elks swimming with only their noses above the water.
Objection: Can never swim as fast as Storsjöodjuret.
Theory: Temperature inversion. An optical illusion where a warm layer is created on the surface of the water so that refraction is distorted. A stick can be enlarged to an animallike object.
Objection: This does not explain the fast swimming action so often described.
Theory: A large fish - a Sheath fish.
Objection: No sheath fish has been caught north of lake Mälaren. Sluggish animals that live most of their lives in the mud do not behave like Storsjöodjuret.
Theory: A whirlwind that sucks up a bubble of water and moves swiftly across the surface of the lake.
Objection: Whirlwinds of this strength are unknown in this area.
Theory: A tree with roots attached.
Objection: Too lifeless.
Theory: An unknown seal species or survivor of a since long extinct sea-reptile of the mesozoic or secondary period.
Objection: Interesting but unproven theory.
Theory: Porpoises that are said to have escaped from a menagerie in the harbour in the 1890's.
Objection: Storsjöodjuret existed long before this!
Theory: Waves from a bypassing boat
Objection: For an unexperianced observer this could be associated with the Monster. The Monster itself make similar waves.
