Snorkeling is possible in almost any body of water, but snorkelers are most likely to be found in locations where there are minimal waves, warm water, and something particularly interesting to see near the surface.
Generally shallow reefs ranging from sea level to 1 to 4 meters (3 to 13 ft) are favored by snorkelers. Deeper reefs can also be explored, but repeated breath-holding to dive to those depths limits the number of practitioners, and raises the bar on the required fitness and skill level. Deep diving should only be done using a buddy system.