Moon Snails are fascinating creatures (unless your a clam)        Here is more information ... 

Locomotion

The moon snail's foot not only helps it to glide along the surface but also to dig in the sand or mud. Most of the animal's time during the daylight hours is spent buried in the bay bottom.

When a moon snail "digs in" the tip of the foot is inserted into the sand. The snail then pumps water into the underground part of the foot. Acting like an anchor, it is then contracted. As this happens, the foot pulls more of the body down into the sand with it. This process is repeated and as more of the foot is dug in more of the foot is filled with water until the snail is buried under the bay bottom.

Once the animal is buried it can move underground by selectively filling different parts of the foot with water to pull it through the sand.

Movement below the bottom can help in avoiding predators and more importantly being where the calms are.                                                               

                                     Click on any image to enlarge

Reproduction

Like all snails, moon snails reproduce by laying eggs which hatch as larvae and develop into tiny replicas of their parents.

A female moon snail will lay thousands of eggs which are encased in a structure called a sand collar.

The process starts with the female expand her foot to cover her entire shell.  Cilia on the foot pick up grains of sand and disperse them over her body until it is completely covered.

She then uses mucus to cement the grains of sand together to form a layer of of flexible material which now surrounds her body.

She now starts to produce the thousands of eggs using cilia to distribute them evenly them between her flesh and the sand layer.

A second layer of sand and mucus is produced in the same manner as the first and placed over the eggs to form a thin "sand sculpture" of two layers of sand/mucus with the eggs sandwiched between them.

When finished, the snail leaves the sand collar by digging into the sand and moving away from underneath it.

These egg masses often wash up on sandy beaches, either whole or sometimes in fragments. When they are whole, sand collars are shaped like an old-fashioned detachable shirt or blouse collar (hence the name).

A fresh sand collar feels stiff and yet flexible, as if it were made out of plastic. After the eggs hatch, the sand collar becomes hard and brittle and eventually disintegrates.