Hi Meredith - oh yes, the Florida Retreat was fun! I'm glad you took some time for a walk on the beach.
The best product I have found for preserving sea shells and giving them a permanent "wet" appearance is Krylon Crystal Clear Acrylic Spray. Not a paint, this spray is a safe and easy way to preserve many organic items, even dried flowers! Of course, always read the product label first, work in a well-ventilated area, and to avoid fingerprints, don't touch your shells until they are dry. (When I lived on the beach, I would string my shells on a piece of fishing line, then hang it from the clothesline while spraying, and then just let them dry for about a half hour.)
Krylon's "Spraying Safe"
article has great tips on working with sprays. For further information about the safety of the product, the Material Safety Data Sheet (MSDS) is available on the Krylon product page. Once dry, the coating is completely safe.
Answer contributed by Dale "Cougar" Armstrong