Lake Grensvatn has an area of 0,3 km². Since 1989 brown trout has successfully been released into it. The number of permits issued per day is between 5-8.

The catch consists solely of brown trout,1-3 pounders. The best fishing spots are at the mouths of the brooks and the northeastern part. It is possible to get within 500 m from the lake in 4wd vehicles.

The distance from the capital is 186 km  by the Whale Bay tunnel and 13 km from Laugarbakki.