Bilateral symmetry is the arrangement of body parts into left and right halves on either side of a central axis. When an organism is bilaterally symmetrical, you could draw an imaginary line from the tip of its snout to the tip of its back end, and on either side of this line would be halves that are mirror images of each other. Many animals, including humans, exhibit bilateral symmetry.
The term bilateral can be traced to the Latin bis ("two") and latus ("side"), while symmetry comes from the Greek words syn ("together") and metron ("meter").
Many marine creatures exhibit bilateral symmetry. Examples of marine life profiled on this site that exhibit bilateral symmetry are: