Creepy Crawlies

If you spend much time at the coastline, at least here in Florida, you'll see these little critters pretty often. Whenever you approach some rocks on the waterline or maybe a dock or something, you'll see them scurry away from you so fast that you can't get a good look at them. Well, I got lucky and came across some that weren't as scared as they should have been, and I got a picture. Now, what are they? Not sure. I've heard them called different things, but I think sea roaches is the most common. I'm sure they have a real name, though. Wharf roach, maybe?