Rømsjøen, or Rømmen as it used to be called, is a small lake in the county of Østfold in south-eastern Norway. It’s close to the Swedish border, and not far from the hamlet of Rømskog. Though it is the biggest lake in the area, at 14 sq km (5.4 sq m) it is smaller than most other ‘monster-lakes’.

As well as being rather small, Rømsjøen is not at all well known as a monster lake, even in Norway. Seljordsvatnet, with its ‘Selma’, is probably the most famous, but many lakes in Norway have had – and still have – sightings of the so-called “sjøorm”.