January 16, 2002
This photo of a beach near Panama City, Florida was taken at night, near the time of low tide, and shows the beach area referred to as the "swash zone." This is the part of the beach between high tide and low tide, so it's underwater about half of the time. The swash zone is alternately covered by the upsurge of water (swash) and exposed as the backwash retreats. A number of organisms depend on the swashing of the waves to provide them food and shelter. For example, this part of the beach is home to sand crabs, lugworms, bristle worms, and ghost shrimp. All of these have been able to adapt to periods of submersion and exposure to air. Some large two-legged organisms also spend a good deal of time in the swash zone. These rather clumsy critters are, in general, detrimental to the health of the beach and shore.