When you book a channel crossing, most experienced pilots will want to know how fast of a swimmer you are. Can you repeat 20-minute miles, 25-minute miles, or 30-minute miles? A pilot will often want to start a faster swimmer at a different time of day (and in some cases, a different location) than a slower swimmer.
But what if you train mostly in a pool? Do you give the pilot your best 1,650 time?
The problem with trying to estimate speed in the open water from pool times is…well, lots of things. But one of the big ones is turns. If you gain 1 second every time you push of the wall in the pool, that’s 2 seconds per 100 long-course and 4 seconds per 100 short-course, compared to the equivalent distance in open water.
So, if you use a straight conversion of distance-to-distance, you’ll probably over-estimate your open water speed (unless you have really slow turns). Here, then, is an open water pace table that factors in time gained from turns. It assumes 1 second gained per wall - some people gain more and some people gain less, but I think it’s a reasonable approximation.
This pace table converts between pool pace times (100 short-course yards or 100 long-course meters) and open water swims of various distances. The conversion assumes 1 second gained per wall in a pool (4 per 100 SCY and 2 per 100 LCM).