This waterfall, which my maps lead me to believe is Rjúkandi, is situated just 3.5km east of Ólafsvík on the western side of the Snæfellsnes Peninsula. It's easily noticeable as you drive by on the road 574, but I'm not sure if the road to get closer to the falls is official or not (i.e. we're not sure if we were on someone's driveway). Pretty interesting waterfall nonetheless.