Assateague ponies, made famous by Marguerite Henry's novel "Misty of Chincoteague" and it's sequels, aren't always hanging out close to the trails.
There are several outfits that offer pony watching tours by boat where you can get much closer to the horses than we did.
Still, the MD end (National Park section) is great for short walks and you can camp on the island. We didn't check out the back country because we were heading for the VA end well and didn't have time since you can't drive straight down the island and have to go back to the mainland.
The VA end of the island has more developed facilities and a few longer walks. You can't camp on Assateague in VA so you have to go to a private campground on Chincoteague Island.
When we were camping on Assateague in 1956, we saw ponies. I don't know about the status in 1956, but now the horses are split into two main herds, one on the Virginia side and one on the Maryland side of Assateague. They are separated by a fence at the Virginia/Maryland State line.
These are my parents photos of the ponies taken in 1956. In those days you could not get close to them.
After all the hiking, the family wanted a chance to dip their toes in the Ocean. Parking for North Ocean Beach was plentiful early in the day, and they do provide changing areas and a pump to wash your feet off of sand. From the parking lot, there's a new wooden bridge that carries you over the dunes to the beach, then you can cut across the fairly pristine sand to the water. There are a few lifeguards on duty here as well. Many people were setting up for a long day at the beach - we just stuck around long enough to get a little wet, but this looked like a great place to spend some time.
The first trail upon entering the park, but we saved this for last (mainly because I missed the turn off for it.) The first tip - reapply your repellent again. Like the others, this trail is a loop trail that is about a half mile long. This one is mostly raised boardwalk through the marsh, mostly open marsh land (as you can see from the photos.) Those with smaller ones need to keep an eye open, as the boardwalk has no real railings in most places, and you're open to the water areas. About midway through the trail, you can take a small detour off to an overlook, which also has a brief staircase down to the bay. From a hiking standpoint, this one is pretty easy, and I found the scenery the best of the three.
The final trail before you run out of road, this is easily the most difficult. Again, the length is only about a half mile, but the bulk of it is over very loose sand. This is very tough hiking as a result. Also, there is almost no shade, so on a sunny day, this probably is pretty brutal. The landscape is a little more stark here, the wildlife was pretty non-existent. It took us about 20 minutes to do the loop trail. At the end, we dumped about 3 pounds of sand from our shoes. If I were to pick one trail to skip due to time constraints, I'd go with this one.
There are three small trails at Assateague, each equipped to give you a flavor for the types of environments in the area. None are particularly well marked, so keep an eye on the map, and you'll be able to figure out where to stop. The second trail after the entrance is the Life of the Forest trail. This is about a half mile long, mostly on boardwalk, with a scenic overlook about halfway through. Be sure to apply mosquito repellent, because the land is wet, and the bugs will bite! You'll start off going through the forest (of course!), but you will get a break a little way in with a nice view of the bay. While the scenery is not the most spectacular, we were able to see a few horses, and a number of bugs and flowers that were of interest.
Try your hand at live clamming, the best method seem to be raking. The water in the bay is rather shallow so wading is no issue. There are a few types of wild oysters that can be found around Assateague. Careful you do not trespass on leased oyster bed, it's best to stop at the visitors centers for more information on the top spots. Also you can only take what you can eat right away.
If you go down Bayside Dr. to the end, on the right side there is a canoe rental place. There is a lot of area to cover, with many small island to stop on, plenty of nature to photo! You can touch the bottom at all most any point in the bay, so no worry is you tip the boat over. Explore this great place and have fun.
Looking for some thing to do here, go find a nature trail, there are several. Go down the main road to the Natioal Seashore entrance and you'll find the Shipwreck history, forest trail, marsh trail, and the dunes life trail. All of these trails have parking right there and are pretty short walks with plenty of information about the island and it's history.
If you drive on to the island go to the National Seashores entrance to access the beaches, camping and four wheel drive access point. We stopped at North Beach and walked to the beach and there were at least 25 horses in the area.
The ponies of Assateague are not just a "must see", they are a "will see". There are almost always five or six of them right on the other side of the bridge from the mainland. If I didn't know any better, I'd say that they were park employees, stationed there to greet new visitors.