I have a series of open water swims where I lose GPS very frequently (not sure if it is me or the watch)- and it calls all my swims short. The map looks like the route I swim, but when I swim in and my wife swims the same route we get a massive difference. For example- I swim 1 lap of the local lake (measured at 1.35km) and I get 0.9km and she gets nearly 1.4km. Is there anything I can do to correct the distance without losing the map etc? I have tried adding a course, but this doesn't seem to work. Any one have any ideas?