The accident, where Aksel Hennie rolls his Jeep isn't staged, but a real not planned rollover without a stunt man. Hennie was to drive off the road, and make a Sharp turn, but the Jeep wasn't able to perform such a turn at that speed, without rolling over.
The video player in Petter's houseboat is a Philips Video Cassette Recording System, an early home video format in Europe in the 1970s.
The large underwater welding enclosure, on set was a stand-in, which was essentially a box with a big tube over the top of it. A crane moved it around so that everyone could see it, but it looked absurd. In the film it was digitally added.
About 1 hour into the movie you can spot the AdO-arena, the swimming hall in Bergen city, in the background. The movie is supposed to take place in the 80's, but the swimming hall wasn't build until 2014.