They are mostly Shrimp boats. There are a ton of them around here (Galveston Bay, Texas) There are also a lot of Oyster boats around here, but don't see any in that pic.
I've attached a pic of a shrimp boat that was in the yard at the same time so you can get a better look. Interestingly, this one is owned by a young couple, in their 20's. His Dad has a shrimp boat when he was growing up and he always wanted his own boat. It's a steel hull, and he was using a grinder with a wire brush attachment to take the entire hull to bare metal and using coal tar epoxy to seal it back. He is a tough kid, as that entire lifestyle is back breaking work! He was doing all this work himself, with a little help from Dad.
Hey, Boogiediver,
That's an interesting cradle that they are lifting your boat out of the water with. Is that a universal thing, or just made for that boat in particular? Never seeen it done quite that way.