Summarize the following:
Seashells can either be gathered from the beach or purchased at a craft store, or you can buy synthetic or artificial shells. While artificial shells may not have the same natural appeal, they are better for the environment.  Seashells play an important role in coastal ecosystems, and provide homes to algae, birds, and hermit crabs. Removing shells from the beach can have a detrimental impact on the creatures that rely on them.  If you really want to collect your own shells, only take a couple from each beach, and never take shells from highly visited beaches where others are often collecting shells. Always inspect each shell to ensure a hermit crab hasn’t claimed it for a home.  Shells are also a byproduct of the fishing industry, and there are some shell suppliers that only obtain shells from these producers. Buying shells from these producers could have less of an impact than purchasing ones collected from beaches. Natural shells that are collected from the beach need to be cleaned to remove dirt, particles, odors, and bacteria. The most common way to clean shells is to soak them in a bleach and water solution:  Fill a bowl with one part bleach and three parts water. Soak the shells for anywhere from 30 minutes to 24 hours, until the leathery covering—called the periostracum—comes off.  When the shells are clean, use a soft cloth or soft-bristled toothbrush to give them a gentle scrub, then rinse them well with clean water. Allow the shells to dry. You don’t actually have to do anything to preserve the shells, but if you want to enhance and protect their shine and luster, you can polish them with mineral oil. Use a lint-free cloth to rub a small amount of mineral oil over each shell, and gently polish the inside and outside. Since you'll be using the shells for jewelry, another option is to protect them with a thin coat of satin-finish polyurethane varnish. Apply a light layer of varnish to the inside and outside of the shells using a clean paintbrush. Allow the varnish to dry completely.

Summary:
Obtain seashells. Clean the shells. Preserve the shells.