Hey Rob,
Go down to your local electronics store and buy a USB -> SD Card reader, as well as a 1 Gig SD Card.
Plug the card into your GT-31, set it up according to this page:
http://gpsteamchallenge.com.au/guides/setupgt11_2008.phpNow after going sailing, take the SD card out, plug it into your card reader, and save the file to your home folder.
Open up GPSActionReplay (
gpsactionreplay.free.fr/), get it to read your file, and you'll be sorted.