Curragower Falls is in the heart of Limerick city under the shadow of King John's castle. The falls are formed when the river Shannon drops over a rock ledge when the tide is falling. During the winter (November to April) when the river is high, the volume of water and the combination of low tide turn the falls into a freestyle playground for kayakers. Around 3 hours after high tide (Limerick dock , www.sfpc.ie) the waves begin to form. Reference: http://playak.com/article.php?sid=1200