Garmin MK2 seems rusty after 5 months of use

I'm a Divemaster and I make about 3-4 dives a day. Also like to run and hike a lot and I wanted a GPS watch that can do all that stuff but also be a good dive computer.... And of cource Garmin is the only company that has achieved that so far.

The problem is that the stainless steel model rusted after the first month of heavy diving use and recently I have noticed some rust at one of the "goldish" charging contacts.

I wash the watch with fresh water after every dive but unfortunately it rusted around the buttons and at one of he contacts and that last made me to search if other have the same issue with this watch that is built to be in the water!