WATER TESTING AT PRESTON:
The water is tested for e coli. every Wednesday by the Swampscott Board of Health. Results are available on Thursday. It is tested in the surf 4 feet out.  The Swampscott Health Department believes the problem is that in a heavy the rain runoff washes animal waste through Hawthorne Brook and out the culvert into the water at our beach and that it takes several days for the tide to disperse it.
http://mass.digitalhealthdepartment.com/public_21/beaches.cfm?bID=12401&func=details

 http://mass.digitalhealthdepartment.com/public_21/faq.cfm#6

TIDE CHARTS:

Here's a nice site with a clear graphic that shows the tides for the week:
http://www.freetidetables.com/state/Massachusetts/sid/2113cb72

For your convenience, here's a tide chart for June which includes sunrise, sunset and the moonphases:
http://www.boatma.com/tides_new/tides.pl?type=calendar&location=Lynn%20Lynn%20Harbor%20&month=June

GREAT PHOTOS and text about the beach BY DENNIS CURTIN:
http://www.shortcourses.com/Preston-Beach.pdf

The following is taken largely from Discovering Marblehead: Historic Places, Open Spaces

    Preston Beach, known as Preston-Phillips Beach by Swampscotters, stretches almost exactly a mile from Marblehead into Swampscott (the Swampscott portion is 5260 feet long). 

   Even in winter, when high tides keep it clear of snow and ice, this level, smooth expanse of sand is ideal for walking, jogging, or watching a spectacular sunrise over the ocean. The only drawback to this daily “cleaning” is that most of  the beach is covered at high tide and you can only walk its length at mid or low tide.

    Rocky headlands anchor the beach at both ends and shelter tidal pools full of marine life. Look here for hermit crabs, anemones, sea urchins, and sea stars. At the Marblehead end, where the beach is gently sloping, small sand-filled tidal pools often form at low tide. They provide a safe swimming area for young children—shallow, free of waves, and much warmer than the ocean.

    At the Marblehead end, a small, publicly owned part of the beach can be reached by a sea wall. This walkable wall runs between the beach and Surf Street and Spray Avenue—both well named since the surf
pounds against the wall during storms, sometimes sending water higher than nearby rooftops.

     On a clear day you can see the south shore beyond Boston, and on a clear night at least three lighthouses: Graves Light, the Boston Light and Scituate Light.
   
    Storm drains at each end of the beach discharge water onto the beach. Children .. should not play in this water, however, especially after heavy rains when the fecal coliform count skyrockets, mainly from dog [and other animal droppings. The runoff also contains poisons such as asbestos from brake linings, pesticides and herbicides  from homes and the Tedesco Country Club. 

HISTORY AND SETTING


Since the glaciers melted back, the beach has gone through a number of stages. At one time it was dry land and at other times a marsh. If you walk from the Marblehead end of the beach toward Swampscott immediately after a storm, you may see the exposed  root systems of large trees. In an earlier era, a shore lined with trees ran down the middle of the present beach. Well below today’s high tide line, the root systems show how far the ocean has risen (or the land has sunk) in just a few years—at least in geological terms. Beds of clay, both gray-blue and yellow, are also occasionally exposed. These clays resulted from fine sediments being deposited in the still waters found only in protected ponds and marshes. Finally, you will sometimes see layers of peat, formed by vegetation that drifted to the bottom of the marsh, where lack of oxygen prevented  decomposition .

Flirtation Rock is a geologic museum with some of the most interesting geologic features you will find anywhere. Long parallel scratches in the rocks, obvious in the right light to even the most casual observer, were caused by glaciers passing over Marblehead as recently as 15,000 years ago. The scratches on the boulders were caused by the moving glaciers and point in the direction the ice was
flowing

As you stand on the beach or walk its length, you may catch a glimpse of seals. Though it is not a frequent
occurrence, they have sometimes been sighted swimming offshore. Also offshore is Ram’s Island.

Flirtation Rock is well worth exploring. It is here that you will find the many tidal pools full of sea life. Colonies of barnacles crowd along the base of the rock. In tidal pools you can find large groups of periwinkles, anemones, and red algae. If you sit quietly and observe patiently, the pool will come to life. Hermit and other crabs scuttle about, and small fish dart from their safe hiding places. You can even see the barnacles open to sieve the water for food. A casual glance is never enough.

At the end of Flirtation Rock the waves crash into a deep crevasse with a round cup-like depression at the bottom, carved out by rocks moved in circles by the waves. Look down into this pool and you will often
see large crabs, as big as your hand or bigger.

Danger

Climbing on any rocks can be dangerous, but seaside rocks are especially so. Avoid any wet areas or black areas even when they look dry. These black areas are blue-green algae and are as slippery as ice. One
way to stay safe is to check that each new foothold has traction before transferring your weight to it.

The Strand Line

When the tide touches the highest point of its upward reach and then begins to retreat, the last waves at this highest point  push flotsam and jetsam beyond the reach of the waves that follow. This line of debris is
called the strand line. Usually there will be more than one strand line, since tides rise higher or lower depending on the position of the moon and the sun. The highest tides of the month, called spring tides, create a strand line that cannot be erased by subsequent tides during that month, so it remains until another spring tide reaches high enough to move it. The highest strand line on the beach is really an outline of the highest previous tide.

The strand line is the place to look for things washed in from the deeper ocean. Amongst the dried seaweeds, like rockweed and kelp, you will find jellyfish and a variety of shells. Underneath, beach hoppers and sand fleas burrow into the moist sand. You might find a skate egg case. Often called a mermaid’s purse, it comes in two sizes. Those up to about 2 or 3 inches long are from the Little or Big Skate. Larger ones of 5 inches or so come from the Barndoor Skate, which is  slowly becoming extinct in this area. You can usually locate an opening in the case through which the skate exited. The tendrils at each corner originally attached the case to seaweed in deeper water offshore.

Palmer Pond

        At the Swampscott end of the beach lies the 17.75-acre Palmer Pond Wildlife Conservation area (once known as Cedar Swamp or Long Pond) managed by the Swampscott Conservation Commission. This area
actually contains two ponds, separated by a path that allows you to get close to the water and maybe catch a glimpse of muskrats and migratory birds. The pond was originally a coastal salt marsh, but drifting sand has created a barrier beach that isolates it from the ocean. However, there have been years when winter storms breached the sand barrier and flooded the pond with salt water. Occasional fires or storms disrupt the sand-covered surface of the land and reveal layers of peat, laid down when the area was a marsh.
         Palmer Pond is a stopping off point for waterfowl, where you will see mallards, black ducks, coots, herons, rails and other migrating water birds. It is also home to muskrats, turtles, frogs, and small fish. The vegetation includes extensive cattails, duck weed, and beach rose (Rosa rugosa), a native of eastern Asia that stabilizes the sand dunes. The Palmer Pond area is full of beach rose (Rosa rugosa) and poison ivy.
         On the ocean side of Palmer Pond (once known as Phillip’s Pond) are sand dunes, not very impressive, but the only ones in the Marblehead area (until a new one has been created by order of the DEP contiguous to Beach Bluff Park.) In these dunes, you can find plants typical of those found in more developed dune systems which have the ability to resist desiccation and survive burial in sand.

         Past Palmer Pond is the Swampscott headland known as Phillips or Littles Point, which is full of interesting rock formations and tide pools alive with sea life. Littles Point is another excellent place to explore tide pools and fascinating rock formations.

The Winter Beach


         The gently sloping, smooth expanse of Preston Beach in summer turns into a much steeper, boulder-strewn beach in winter. Even the entrance to the beach at the foot of Beach Bluff Road becomes a near- wall of cobbles. This illustrates one of the seasonal cycles that affect all beaches—especially those exposed to the force of nor’easters. The change in the beach is brought about by a change in the 8,000 or so waves  that strike it each day. In the summer the waves generally are low, wide, and spaced far apart.       These low energy, rhythmic waves pick up sand from the bottom offshore and carry it to the beach where it is deposited, gradually filling in and building up the beach.
          In the winter, storms occur more frequently and their higher, steeper waves, spaced much closer together, lift sand off the beach and hold it in suspension. As the waves then recede back down the beach, they retain more energy than summer waves, and are thus able to carry the suspended sand out with them. When the waves reach the quieter offshore waters, they slow down and drop their loads of sand. Eventually this process builds an offshore sandbar running parallel to the beach. It is amazing how fast this cutting action can take place in a winter storm. One storm can transform the beach from its summer shape to its winter shape in a matter of hours. The sand then remains offshore until the summer waves begin again to slowly move it back up the face of the beach in this never-ending cycle.
           During the winter the smooth sand beach is covered with rocks and boulders that are exposed when the winter seas move the sand offshore. Little sand is lost during the annual cycle that moves it between the beach and the offshore bar and back again, because the long shore currents that run parallel to the beach are weak. However, there is some movement from the Marblehead end of the beach to the Swampscott end, and it is this current that built the barrier beach in front of Palmer Pond. The cutting action that creates the winter beach also reveals what is below the sand—and transports us back in time.

Marks on the Beach

    
If you walk the beach at low tide, you can see a variety of marks left on the sand. In ancient deposits, where the beach has been buried and consolidated into stone, geologists can use these markings to learn much about the beach they came from. Swash marks are left when the wave washing up the beach reaches its farthest point and drops its load.
          The materials in this line are usually coarser sand with black mica flecks, tiny bits of shells, seaweed, and other debris. These marks show only on the upper part of the beach, below the strand line and  above the water table runout, which obliterates them on the lower beach. Since their convex shape points shore- ward, geologists can tell the orientation of ancient beaches.
          The water table runout is water in the sand that flows across the surface and back to the ocean after the tide has fallen. As the water runs out from beneath the sand on the upper beach, it creates rill marks on the wet surface of the lower beach. The individual branches of this miniature gully system join into braided streams at the shoreward end, another indicator to geologists of the orientation of an ancient beach. Current crescents and V-swash marks appear when the backwash is deflected by a pebble, shell, or other obstacle. A shallow crescent scour is formed on the upstream side and an inverted V forms downstream of the object.

Human Impact

As recently as 1950, horseshoe crabs were very common on the beach, starfish and anemones were plentiful. High tides reached only part way up the beach, while today they crash against the seawall. These changed phenomena point to the impact of increased oxygenation of the sea, warming of the waters, pollution and other changes caused by human activity.