Skim Some Stones

Find a river or lake with some small, smooth stones you can skim across the water. See how many 'skips' you can do or how far a stone travels or how accurately you can skip your stone to an object.
A fun variation of this challenge is throwing 'skimming stones' straight up so they land in the water via the thin side and make an amazing 'chilkk' sound - with no splash.