Just prior to a female moon snail laying her eggs, she prepares a structure called a sand collar to house and protect them until they hatch. The female sinks to the ocean floor, rises above the sand and covers herself entirely with her large foot. The cilia on the outside of the foot grab onto grains of sand and pull them onto her body until she is covered in a layer of sand. The female secretes mucous that hardens, causing her to be encased in a hard, plasticlike shell of sand.
The female snail produces thousands of eggs and lays them at night. Her body again uses the cilia to distribute the tiny eggs evenly between her skin and the hardened sand collar. Afterwards, she uses her cilia to create another layer of mucous-hardened sand, this time between herself and the newly-laid eggs. She then burrows down under the sand collar and heads off in search of food. Due to the incredible amount of energy the mother moon snail expends during this process, she is ravenous and thus, relentless in her search.
The eggs within the plasticlike structure of hardened sand begin to hatch in a few weeks. As they emerge, the sand collar that protected them disintegrates. For a short while, the baby snails are planktonic larvae.
When their shell begins to form, the young snails travel to the bottom and search for food. The cycle begins again. As a young moon snail's shell grows, it forms around a center line, or axis, and creates a tube. This gives the snail its unique spiral shape. The tube running through the center of a snail's shell is called an umbilicus. A moon snail's lifespan is from two to seven years. When they die, their shells are generally taken over by hermit sea crabs.