I went to the Outer Banks in July. It was beautiful and by far my favorite place to be. Running at the beach is challenging because it is vacation so I only want to sit on my butt, drink a beer and read a book. You have to wake up early (6AM) to run because it is so hot. I ran 3 times. one 4 mile run on the road and 2 30 minute runs on the beach.
Have you ever run on the beach? It is a BUN KILLER. My thighs and butt were so sore, but it was awesome. Trying to stay stable, breathing in the salty air, hearing the waves crash and running with my sister was great. I never see her because I live so far away. She is an amazing runner and the reason that I run today. She runs super fast, like sub 1:45 1/2 marathons but she slowed it down so we could run together.
I miss those runs and can't wait for next year. What is the most challenging terrain you have run on?
Also, I got sweat in my eye balls, which is the greatest thing EVER. I love it because it means I worked out really hard. It happened every day at the beach and at Williamsburg.