River Chanctonbury                                     -      -      - 
(-------------------------------------------------)     - <---(M)---> E
                                                        -      -      -

As you get swept along by the current, you bob up and down lots, quite
like a cork.  On one of your trips to the bottom, you see three or four
Salmon swimming upstream quite easily, and wonder "How the Heck do they swim
against this?"  As you contemplate that for a second, a rock sneaks up on
you from nowhere and blacks you out for a minute as you continue downstream.