Starting as swell on the surface of the ocean far at sea, energy transferred to the water by wind moves in all directions. As swell gets closer to shorelines it begins to encounter the bottom and form into a wave that breaks on the beach. Differences in the depth along a beach causes the waves to change direction to match the shape of the beach.
Reef-building corals are a partnership of an animal and single-celled algae that form a partnership capable of forming structures of biological origin that can be seen from space. The animal harbors the algae in its tissue, providing protection and a source of fertilizer for the photosynthetic algae. The algae reciprocate by sharing excess materials produced by photosyntesis.