The Foretrex 201 fits in an Aquapac, it`s a waterproof pouch that has a strong wide velcro strap, so you are not relying on the watch-style pins to hold it on if you have a big wipeout, as we often do while windsurfing (most guys use this unit for speedsailing). Attached is a pic...
Also many have commented on windsurfing forums that it`s necessary to keep it in this pouch as high impact wipeouts can force water into the unit under high pressure, while it was designed to operate underwater to a reasonable depth, the pressure exerted on it is far higher when attached to your wrist or upper arm and you are flung into the water at high speed. Added bonus is that the Aquapac seals in air and floats if you do lose it, something the unit won`t do alone.