The sun and surf that welcome us to the beach are the very things that discourage animals and plants (and people) from making a home there. The sun can bake the sand until it feels as hot as the desert. Waves and wind constantly move the sand, making it impossible for plants and animals to find a permanent home.
Several thousands of waves a day attack a beach. Waves drag the sand grains up and down the beach in a zigzag motion. People who live near beaches know that the waves carry away sand, usually from where it's wanted, and deliver it someplace else, usually where it's not wanted! Some home owners built seawalls and other barriers to keep the sand in front of their beach. Seawalls may hold the sand in front of one home but rob sand from a neighbor's beach further down the coast. Nothing works for long. One winter storm can wash away a month's work building a seawall. It is now illegal in Maine to build seawalls and homes where they will be threatened by waves.
For animals which must find a home on the beach the best strategy is to dig in. The sharp shells and long foot of the razor clam can tunnel through several feet of sand in seconds. Razors, soft-shell clams, and quahogs draw in food through their long siphons ("necks") so they can eat while hidden. Large gills allow them to breathe under the moist sand. Sand worms excavate deep U-shaped tunnels. Sand dollars barely cover themselves with sand. Meat-eating moon snails plow through the sand looking for clams and periwinkles to drill and devour. In the spring the mother moon snail deposits a delicate sand collar of sand and glue as her egg case.
The strand line is where dead seaweed and empty shells collect at high tide. Here are the remains of those that lost the battle with the sea. But look closely and you can find sand shrimp and beach fleas hopping through the debris.
Above the high tide line, beach grass anchors the sand dune in place. It is called the "guardian of the shore." The long roots and underground stems of the beach grass dig for water deep under the sand. Its long, spiky leaves bend with the wind. Other beach plants have thick, waxy, or fuzzy leaves that resist drying out by wind, sun, and salt spray.
Maine has only about 7 miles of sandy beaches along its coast. Most of those are in southern Maine towns such as Ogunquit. Each year tons of garbage, mostly plastic, are picked up off the beaches in an annual beach clean-up during CoastWeek. The people who help feel that, like beach grass, they have to be "guardians of the shore."
Collect sand from several beaches and from river banks. Use a hand lens and a toothpick to separate grains. Most of the sand is made of clear, glassy quartz. Other minerals you may find are feldspar (pink or tan), hornblende (black and dull), and mica (shiny and flaky). Add a drop of vinegar to the sand sample. If it fizzes, there are probably shell fragments present. Compare sand sizes (beach samples will usually be finer, worn down by wave action). Make a sand painting by gluing sand onto a picture.