Water refracts light very differently from air, which is why your eyes don't focus underwater and everything looks fuzzy. The mask provides an air pocket that allows the eyes to focus properly. While goggles do this too, they are more prone to leaks, more liable to being knocked off the face in rough waters and they cannot be equalized for pressure on skin dives. Snorkelers often skin dive to depths of 30 feet or more, and water pressure at that depth pushes hard on the mask. That can give you a bad case of "mask face" or even crack the mask's lenses. Because a snorkel mask has a nose piece, you can exhale a little air into it that will push back against the water pressure and equalize.
Fins are necessary for snorkeling. They increase the surface area of your feet so you can push against more water when swimming. That greatly increases your propulsive power.
The snorkel is usually clipped onto the mask's strap. The main benefit of the snorkel is that it lets you look down into the water at all times while continuing to breathe normally. Most snorkels are simple tubes, but some come with extra features that are meant to make breathing in rough water easier. Waves tend to splash water into the snorkel, so many snorkels come with guards on the top or one-way valves that block water from getting in. Another feature is a sump at the bottom of the snorkel. This is sometimes augmented by a purge valve, which expels the water out of the snorkel.
Wetsuits are often worn by snorkelers even in relatively warm waters. You might spend 30 to 45 minutes in the water, which is different from going for a swim at the beach. With that kind of lengthy immersion, even water that seems warm can become chilly, and in colder waters, a wetsuit becomes even more necessary. Wetsuits are also buoyant and therefore serve as a minor swimming aid.
A snorkel vest is an inflatable device similar to a life jacket. Wearing one reduces the energy you need to spend on swimming, which is a major benefit for weaker swimmers. It has a valve for manual inflation and deflation so you can let the air out if you want to go on a skin dive.
Article Written By Edwin Thomas
Edwin Thomas has been writing since 1997. His work has appeared in various online publications, including The Black Table, Proboxing-Fans and others. A travel blogger, editor and writer, Thomas has traveled from Argentina to Vietnam in pursuit of stories. He holds a Master of Arts in international affairs from American University.