This spiraling structure is a fairly common find on our beach.
Kids see this and immediately recognize it: the skeleton of an exotic sea snake! These round rubbery things with the frilly edges, though…
…these are harder to identify. If a kid picks one up and asks me what it is, I’ll have them carry it for a bit so I can talk to the whole group about it the next time we stop.
The first photo, in case you haven’t guessed, actually has nothing to do with snakes. It’s the egg case of a whelk, which some people apparently call a “mermaid’s necklace.” The second one is the egg mass of a moon snail, which is commonly referred to as a “sand collar,” because whole ones resemble old-fashioned detachable shirt collars. To make a sand collar, the female moon snail cements grains of sand together with mucous, embedding her tiny eggs in the matrix. Which means that, after making the kid who picked it up carry it for several minutes, I get to wind up my explanation with “…so basically you’re holding snail snot” and see the look on their face.
Isn’t outdoor education grand?