Nautilus shells spiral with buoyant gas chambers

The nautilus, an ancient cephalopod, uses its distinctive spiral shell to float effortlessly. This shell has gas-filled chambers that the animal precisely controls, adjusting the gas-to-liquid ratio to hover or descend without expending much energy. As it grows, the nautilus seals off older chambers, always living in the newest, largest one. This ingenious system has remained largely unchanged for over 500 million years, allowing these "living fossils" to thrive in deep ocean waters, navigating vertical migrations for food.