Snorkeling masks seal of a path around the snorkeler's face that includes the eyes and nose. This area is sealed off to water, and will not allow water to penetrate the nose or eyes. The mask serves as a window between the snorkeler and the underwater world. Wearing glasses with a regular mask would result in water leaking into the mask where the glasses reach back to the ear, breaking the seal between the mask and the face.
There are masks with prescription lenses available, but investing in a mask of this nature might only be considered by avid divers. Your prescription might need to be altered because the distance from the window of the mask and your eyes is longer than the distance between your eyes and normal eye wear. An eye doctor specializing in sports eye wear will be able to tell you if your prescription needs to be changed. Pre-made versions of these masks are readily available, but will not correct an astigmatism. The masks may be purchased at a diving store.
Fitting Lenses to a Mask
Prescription lenses can also be fit into a regular mask. There are masks with a fixed place in the front to insert these types of lenses. The lenses are slid into the fixed area, clearing the vision of the snorkeler. This type of mask is beneficial in the case of changing prescriptions as a person ages. These lenses can be found at your local sports eye-wear specialist. The masks can be purchased at a diving store.
If possible, some divers prefer to wear contact lenses while snorkeling. However, it is possible to lose them if a mask comes off while snorkeling. Regular contact wearers should keep this in mind when considering snorkeling. Certain contact lenses are not suitable for swimming. These should be avoided when snorkeling. If your contacts do come in contact with the water, they could absorb bacteria that will result in an eye infection.