I have a prescription mask, but while I was working through Divemaster, I decided to get disposable single-day contacts to wear during classes and checkouts. (I wanted to be able to still see when I didn't have my mask on.) I have yet to lose a contact, but there are a few tips that can be useful:
- If your prescription is compatible, get single-day disposables. They even make them in toric for people with astigmatism, although that may be more expensive. If you lose a lens, it's no big deal (bring spares on the boat), and you don't have to worry about what may be in the water. (I don't personally trust normal cleaning to handle everything there may be on a dive.)
- If you can, keep your eyes shut.
- If you need to see, open one eye. Even if you lose the lens, you'll have one left to complete the dive. (If you're doing the monovision thing due to presbyopia, use your non-lensed eye.)
- If you open your eyes with contacts in them, squint. (Honestly, you don't need to actually squint, but the tendency is to open your eye *really* wide when you're trying to see underwater, and simply squinting is much easier than trying to learn how to just look "normally".)
Honestly, if my eye doctor told me that my prescription could not be handled by single-day disposables, I would have asked him whether it can be handled "well enough" for diving. It's so nice to dive with contacts, I'd sacrifice a little visual acuity for the privilege.
Now, sure, I like my prescription mask. I even use it if I'm just hitting the pool for an evening (like last Wednesday, when we swept and vacuumed the LSU Nat). Diving my other masks (with contacts) is just a seahorse of a different color (and a nice one at that).
Lately, I'm using the disposable daily lenses. I'm often diving in an aquarium. My optometrist recommended the change.
When I told my optometrist I wanted daily disposable lenses, his first question was whether I had hay fever or bad allergies. I told him I have no allergies, but rather, I'm a diver. Immediately, he understood (and agreed with) my logic (i.e. no worries about losing them, and no worries about contamination, biological or otherwise).