Interior of Nautilus pompilius

An interior view showing the rigid open chambers within Nautilus pompilius. Although the animal lives in the outmost chamber, a narrow strand of it's soft body penetrates the chamber walls each by a small hole. Nautilus uses the chambers for a type of locomotion. The chambers are filled with both water and gas. When the nautilus absorbs gas from the chamber, the chamber pressure decreases and water enters from outside. The shell becoming heavier and makes the nautilus sink. When the nautilus presses gas into the chamber, water is pressed out, which makes the shell lighter and the nautilus rises, like a submarine blowing the tanks. Unfortunately, because of the beauty of their shell, many nautilus are killed each year for collection and export. Credit: K. S. Matz