AFAIK, the GW-31 is not suitable for windsurfing. Locosys made some prototypes specifically for windsurfing they called GW-51 which were tested by some here. It came up short in a number of areas and was not proceeded with (although it's accuracy @5hz was tested as exceptional in ideal conditions).
They are currently working on a windsurfing GPS with a different form but with very similar internals. I hear it is designed to overcome the shortcoming of the previous proto and will not be in the watch form which was technically very limiting. It may be getting quite close to release.
Watch this space!
The 'Walker' uses the Sirf111 GPS chip, same as the GT-31 so it is most likely discontinued as well due to the Sirf111 stopped production, EOL
