Just because the display is working doesn't mean it's logging. Check you settings, logging should be set to 5hz. And min speed a very low number, ie 0 - 5 kts. Personally I think 5 is way too high I'm still sailing at that speed.
yep, for some reason the default logging is usually x=off.
So if you haven't read the manual, there's some good advice in there.
Wash in fresh water after every sail. it helps stop corrosion on the connectors.
DO NOT press any of the buttons while they are wet. Pressing buttons allows the watch to "vent". If the watch is cold and it vents anything around the buttons gets sucked in. Salt water will corrode the button contacts, rendering them inoperative.