Baby periwinkles (Sea snails).
The very best thing about Cape Cod are the flats. When the tide is low, the ocean recedes from the shore for over a mile, leaving behind a "seeming to never end" landscape of sand bars and tidal pools. It is our favorite time to visit the beach, because as you walk out onto the flats you discover many sea creatures:
(Click on subtitles if you want to see bigger versions)
Underside of a periwinkle. When you pick them up their "foot" is huge, but then it quickly shrinks down and is pulled inside the shell.
Horseshoe crab. Notice how far from the shore we are!
Also, hermit crabs, fiddler crabs, star fish, shrimp, minnows,worms (careful, they bite!), clams, and mussels can be found, with a bit of digging, in some cases.
It's great fun, but I must admit I wear water shoes because of all those crabs!
When you finally get out far enough, you catch up with the sea. The water seems so much clearer out there. We then have a great time splashing, chasing schools of fish and trying to teach our dog to swim.