I'd avoid them if I were you. If you do get one, do not buy the cheaper "knock-off" models. There are major drawbacks if you are a serious snorkeler; you can't dive with them deeper than 8', because you can't equalize them at all since it's full face. A lot of people have had issues (mi empress included) with the ball valve sticking shut while out on the water, this can induce a situation of extreme panic if unprepared to deal with it in deep water. They also scratch really easily since the lens is polycarbonate, the skirt seal isn't great, and there are some other issues I'm not thinking of.

A good quality (and most importantly well fitted) mask and snorkel are the way to go, IMO. You can deal with issues on the water much easier, and it's a more "bullet proof" system.