I am fortunate enough to live only a few hours drive from Assateague State Park. Assateague is actually a barrier islalnd that is bordered by the Atlantic Ocean on the East, and by Sinepuxent Bay on the West side. One end of Assateague is in Maryland, the other is in Virginia. Assateague Island has over 37 miles of beach. The State Park, itself, has two miles of beach that are wonderful for swimming, fishing, sunbathing and looking for seashells. The bayside makes a great spot for fishing and boating.
The biggest attraction, for my family of horse lovers, is the wild ponies that have roamed the island since the 1600's. One cool thing to try to see is the annual pony swim. This is where the ponies are herded and swim across the Assateague Channel to Chincoteague Island where they are auctioned off to help reduce the population. This event is always extremely crowded, though. You will almost always see the wandering horses during a visit to Assateague, so don't feel pressured to go during the pony swim.
There are no hotels on Assateague, only campsites. Nearby Chincoteague has a couple of hotels for those who don't like to camp. Also, Ocean City is a much more commercial beach town if you want all the ammenities and you can still make the short drive to secluded Assategue for the afternoon.This is a basic, back to nature type vaction place. Not fancy, just beautiful!