Natural History Notes: The squid comes up to shallower depths at night using the shell as part of its buoyancy system. A study conducted in New Zealand found that Cook's petrels Characteristics: The internal shell of this deep-water squid is a creamy white coiled tube that expands to a final diameter of around 6 mm. The spiral itself reaches a diameter of 24 mm. The shell is divided into internal chambers which can be seen through the shell.