Put a picture of the beach you visited in a shadow box frame and fill the bottom with sand from that beach. Much neater than a random jar of sand and shells! decorate the frame or put seashells or treasures found on the beach in the shadow box
What to do with your seashells and sand you save from vacations: Buy a shadow box frame and pick a picture from vacation that you took next to the ocean. Place the sand from that beach in the shadow box, add your seashells, sand dollars, starfish, etc.