The answers so far surprise me.  This needs a poll.  Swimming and cliff diving (read on before you flame me...actually cliff jumping feet first and only after carefully checking water depth) is a favorite every trip especally after a hot day (and even when not hot) or a long day sitting in the canoe fishing.  It is absolutely refreshing.  Risks?  I suppose I could drown, but I could drown at the local pool, or wading/fishing in the local river, or in two inches of water in a bucket for that matter, but I haven't in 47 years, so I guess I will assume that risk.  I could cut my foot.  That has happened.  You need to be careful and so far it hasn't been anything a good first aid kit couldn't take care of.  My vote?  Last one in is a rotten egg and who needs a bathing suit?!!