What is the optimal water temperature for a swimmer performance? Are there records of swimmer performance vs. water temperature? I'm not a swimmer but in general I would like to understand if there is specific knowledge about this
I can not comment. Otherwise I would have and most of my answer may be regarded as opinion based.
My children are/were competition swimmers (almost national level) and have the following observations.
- Water is too cold, their muscles can not perform.
- Water is too warm, they can not sweat out their heat (yes, even in water your body transpires heat out!) and this affects performance.
So, it's more a range of temperatures to fit optimal performance ranges. I doubt that it would affect record times as much as being noticeable. Obviously, each athlete has their own optimal temperature range. This would hold for any sport. Having said that, the shorter distances would be expected to have a positive effect of higher water temperatures as you would be able to absorb the heat. Longer distances may even suffer from high temperatures as you can not dissolve the heat.
The regulations (as linked to in another answer) do not state why the temperature needs to be in a specific range. It can not be determined if this is due to less resistance in warmer water or due to the effect of water temperature on bodily performance.