When I go to the beach, I love to look at sea shells. I never take them with me because they're vital to the eco-system. I just gently pick them up, have a close look and sometimes take pictures, then put them back where they were.
It's very important to me not to bother any animals. In the case of certain mollusks like clams and mussels, a closed shell is an indication of life. Barnacles, seaweed and a variety of other living things are easily spotted.
Snail shells are beautiful, varied and interesting, but it's not always easy to tell if there's a live snail inside, especially because they can go so far in that you can't see them.
According to Snail Facts,
The snail can protect itself easily by withdrawing its body behind the operculum that works like a trap door.
Without seeing movement or evidence of a body, how can I tell just from looking at the shell if it contains a living snail that needs to be left undisturbed?