The object in the lower photograph which looks like the hose of a vacuum cleaner is actually an egg case laid by a female lightning whelk. Each one of the discs that is strung together into the chain contains several developing whelks. When they are old enough, the young whelks break out of the egg case and crawl off to begin their lives in the lagoon. You may have come across egg cases like this tossed up on the beach or along the banks of the lagoon after a storm. The various gastropod Molluscs of the IRL exhibit a wide range of diets.
Many species are herbivores, living off algae and plant material.
Another predatory gastropod is the moon snail shown in the top photograph. Like the whelk, moon snails prey heavily upon clams. The bottom photo shows clams which have become unfortunate victims of a moon snail. The tiny holes seen in each of the clam shells were drilled by the moon snail, using a special organ called a radula. Although most gastropods possess a protective outer shell, some of them do not.