I've always wondered this... how do you accurately measure the distance of an
open water swim? Measuring distance over land is usually done with a wheel and
odometer, but what method is used to measure distance over water?
There's usually some error because of the slack between the anchor and the
buoy or the anchor and the boat but it's reasonably reliable.
How about the fact that when the water freezes it expandes, and therefore the
distances on ice are a bit longer, unless the measuring points which are not
on the ice, or in the water.