Animal locomotion refers to the process by which motile organisms generate movement relative to a substrate or fluid. This complex biological function involves the coordinated action of skeletal, muscular, and nervous systems to overcome resistive forces, which can include gravity, fluid drag, or friction. The methods of locomotion are highly diverse, including ambulatory movement across solid ground, propulsive thrust through water or air, and gliding or crawling along surfaces. Underlying all modes of movement are principles of biomechanics, optimizing energy expenditure while maximizing speed and efficiency. Different gaits and structures—such as fins, limbs, or specialized musculature—have evolved to suit specific environments and locomotion needs, demonstrating a broad application of physical laws to biological engineering.