|pictured: Mares Stream Dry scuba snorkel|
Have you seen a whale up close and noticed how it blows water out of the blowhole on top of its head? This physical attribute allows the whale, and all other similar surface skimming ocean mammals, to keep its head in the water for extended lengths of time, while still allowing it to breathe. This allows the whale to swim more efficiently while maintaining the energy level needed for constant motion. A snorkel gives you, the scuba diver the same advantage.
Every scuba diver spends time on the surface while preparing to descend for a dive. A snorkel allows you to conserve energy by letting you keep your head in the water while swimming and enjoying the pre-dive sights without ever having to remove your head from the water.
See our choices for snorkels
A good rule of scuba diving is to always have something in your mouth, your snorkel or your regulator. When you are on the surface of the ocean waves can suddenly swell and overcome you, so if you do not have your snorkel or regulator in your mouth you could find yourself in a life-threatening situation. Your snorkel not only allows you to breathe in unexpected situations, while on the surface, it allows you to conserve the air in your scuba tank for the dive. Choosing the snorkel that is right for you and learning to use your snorkel correctly is one of the most important skills you can learn.
See Also: choosing a snorkel