Paddling in Costa Rica on a high water day is like paddling on top of a bowling alley!  We experienced this phenomena this week when we did a high water run on the Reventazon.  Underneath us, the round boulders that formed the river bed rolled about due to the fast moving high water current racing downstream. The noise is unsettling the first time you hear it.  The loud clanking of the boulders creates a sound that makes you look around to see who just sent the bowling ball into the pins.  Then you realize the sound is coming from below you.  The river bed is alive and constantly moving, settling, moving again. It makes an exciting run even more exciting!!