Lake Krókavatn (Tangavatn) is on the north side of Tvídægra but is still outside the district of the Arnarvatnsheiði Fishing Association and Tvídægra. It is 410 m above sea level and 1.55 km² in area. From the lake on the west side is the outflow of Hrútafjarðará. The access to the lake is difficult and those who are interested in trying it out will need to be prepared for quite a walk. There are Arctic char in the lake, but not much information on how they are caught. However, the lake has proved to be good for passers-by and shepherds, who have taken advantage of a hut by the lake and caught some good fish on a rod.