Hi Floyd, congrats, once you get dialed with GT-31 its easy as 1-2-3.
"Speed Genie" is a program developed by Dr. Tom Chalko specially for "us" windsurfers, it automatically displays current speed while you sail and when you stop depending your configuration it shows immediately: Max Speed, 2 Seconds Max AVG, Max 2 sconds Max speed and you can ad History, Min, etc.
I would recomend you to have a look at http://mountbest.net/setting-up-navi-GT31.htm
this is the best web site for tunning up your GT-31 for windsurfing, follow carefully their steps and your done, I downloaded the new GT31_FW_V1.3B1014a firmware with it new large fonts for "Speed" and "Genie" and now is really easy to read speeds while sailing.
If you are more into full GPS usege take a look at http://www.splitbrain.org/blog/2008-...-31_gps_review
Just my two cents.
PS. Remember to use it inside an "Aquapack"