You can, I did, but that was years ago when I learned to scuba dive. Since then, I'm just a "cruise snorkeler". I haven't had any trouble wearing my contact lenses while snorkeling. If you get a mask that fits well, you won't have to worry about leakage and losing your contacts. Do you wear the inexpensive, disposable type lenses? If so, I would just do what I do and take extra lenses on your excursion, just in case. I've never had to use them, but bring them just in case because I can't see without them!