Foss į Sišu (literally "waterfall at Sišu") is a conspicuous waterfall in Southern Iceland visible from the Ring Road roughly 12km east of Kirkjubęjarklaustur. It's one of the lighter flowing waterfalls so I reckon it has a pretty short season if it hasn't been raining or snowing much. However, being on the south of Iceland, it does rain a lot here so there's a good chance you'll see it flowing. The farms before the falls makes great subjects showing the height of the falls.