At its source in the west, the Måna river flows out of the lake Møsvatn and past the town of Rjukan into Tinnsjå.

Tinnsjå is part of the Skien watershed, and it drains via the Tinnelva river in the south, down to the lake Heddalsvatn.

The Germans were using the ferry to transport a large quantity of heavy water to Germany, where it was to be used for nuclear weapons research.

[7] In 2004, it was investigated and filmed for an episode of NOVA; heavy water samples were recovered and deuterium isotopic enrichment was confirmed.

In 2004, a film crew shooting footage for a new documentary on the heavy water sabotage became aware of an unusual fish, swimming near the lake bottom at a depth of 430 metres (1,410 ft).