There was frost on the car windscreen this morning, the first of the season, but otherwise it was a perfect clear sky morning without any breeze. Honestly though after yesterday when it took several hours for me to warm through after swimming, why am I doing this again?
I must have been especially quiet getting changed on the river bank; where the water flowed by with barely a ripple and steamed with mist (Still Pool living up to its name again), because as I stepped into the water the otter that was sat 10 feet away on the bank obviously got its first hint that I was there. All I saw was the brown shape and sinuous tail sliding quickly into the water and then the trail of bubbles breaking the surface as it swam across the pool: classic! Like a total amateur though I watched the bubble trail thinking it will have to come up soon, but of course it was swimming well ahead of the bubbles so I didn’t see it again.
Until now my aim has been whenever possible to do three times up and back which, depending on the flow of the river gives a distance of between 175m to 205m each way (402m = ¼ mile). If the flow is less the distance is further as it is possible to start from the edge of the downstream shallows and get right up into the top end shallows. However, as the flow increases the shallows flow too fast to swim but though the distance diminishes the effort to swim upstream increases to a tipping point where the river becomes and endless pool and distance is no longer an issue as swim as hard as you like you will go nowhere.
Clearly if the flow is slight and the water is warm (we are talking July) then I could swim up but float back and that would be a zero-sum game where all the added effort put in swimming against the current is wiped out by the free ride back making it equivalent to swimming in still water. However at the endless pool end of the spectrum it is self evidently a non-zero-sum game as clearly if I go nowhere there is no free ride back to detract from the effort of swimming just to ‘stand’ still. But then what about the points in between?
What I have determined from longer sea swims is that my pace is consistently 40m to 44m/ minute. In the endless pool non-zero-sum game scenario in the river the pace is clearly zero meters / minute. Let’s assume then that in the river I could swim at the same pace as in the open sea equivalent to the average of the above figures ie 42m / minute. The assumption is however wrong on at least two grounds which are firstly with shallows and eddies it is not possible to get a steady pace as strokes get missed and secondly head on to a current stifles the stroke making it less efficient. Consequently I will take the 40m / minute figure as my maximum river pace.
In the zero-sum scenario (swim up, float back) it stands to reason that over a given distance my pace should equate to 40m / minute. Anything less than that moves me further into the non-zero-sum scenario to a maximum value where the pace is zero meters / minute.
Actually though what I have found is that even in summer the pace is around 35m / minute and today when the river flow is somewhere between summer and endless pool my pace is about 28m / minute. Furthermore I estimate that when the river is flowing at the maximum rate where it is possible to actually swim upstream that pace drops to 25m / minute and I exit the water feeling very worked out.
Why, you are wondering, is there such a big gap between zero and 25m / minute? It’s a fair point and in a perfect situation it should be a continuum, but the river flows faster and slower along the course depending on shallows or deeper water and where I set off to swim from the current is swiftest and so at all points between zero and 25 I simply cannot start swimming. What I need is a uniform channel with variable flow, maybe some sort of pool perhaps?
And this is what keeps my mind off the fact that I am swimming in 8°C water at 7:30 in the morning where it feels as though my fingers and toes have fallen off.