It wasn't until I moved down-a-shore full-time and took a walk on a winter beach that the answer was revealed: They don't rake the beaches in the winter, and winter storms toss up all sorts of wonderful stuff... Like whole, huge shells. (The downside is that more often than not, there's a lot of man-made trash out there too. I was discouraged from beach walking for awhile because I hated spending my time picking up and hauling off a bag full of trash, but I felt guilty if I left it where it lay...)
My Thanksgiving walk provided me with quite a bit of good photo opportunities (with very little junk!) if not so much in the way of beach combing. The weather has been violent enough that very few shells were large or even in one piece.*
[Clicking on the photos should take you to a photo-scroll with bigger images!]
(I often shoot wide to give myself composition options,
but sometimes I have a terrible time deciding how to crop a photo...)