I wear contact lenses and have dove and swam both salt and fresh water with lenses. Optemetrists highly recommend daily use lenses or using old lenses and discarding them after submerging in any open water situation due to bacteria establishing themselves on/in the lenses.
Freshwater (applies mostly to Florida springs):
Lenses definitely tend to stick if you open your eyes underwater. I have never even had a lens get loose in freshwater. You need to take special care when removing them, especially if you need to remove them soon after a swim. (This also applies to forgetting to remove them before an evening shower.) Copious use of saline in the eye with careful and gentle coaxing should get a contact out in a couple of minutes with no damage. Waiting a while (1-2 hours) should also allow the eye to achieve salinity balance throughout the lens and "unstick" it.
Saltwater:
Lenses don't seem to get stuck, so your health risks are probably less (disregarding general bacterial encroachment on/through the lens). However, I have lost 2 lenses while at the beach, and in the pathetic 2-3 ft surf in Florida. I imagine the problem is more pronounced in area with heavier surf. I always take extra lenses for this purpose. Of course, on my last trip I was visiting family and left my extra lenses at my relatives' house, so of course I lost a lens and had to go "one-eyed" for the rest of the day! If I had $200 lenses, I would definitely use goggles or a mask anytime I was in saltwater, and would carefully keep my eyes closed during any mask clearing drills.
my mask leaks a little, that water stings and I have to blink a lot to cause my eyes to tear and flush things out. However, if I ditch my mask and replace it underwater, I don't have the stinging.
