Skammá is on Arnarvatnsheiði and flows out of Lake Réttarvatn into Lake Arnarvatn stóra. The river has a waterfall which prevents fish from migrating into the river up to Lake Réttarvatn. Therefore, most of the fishing is at the mouth of the river and in several places above. The fishing can be excellent. There is almost no fishing in the river above the waterfall, and it seems that the char doesn’t move from Lake Réttarvatn into the river.