When snorkeling, you swim with a mask and breathing tube at or near the water's surface and observe the reef or marine life below. The breathing tube, or snorkel, sticks up clear of the water and allows you to breathe through your mouth. It's a low-tech, inexpensive way to explore a shallow reef or look for fish along the sandy bottom of any clear body of water. Snorkeling is very simple to master -- all you need is a mask, snorkel, swim fins and knowledge of a few techniques.