Those otterboxes are definitely waterproof. I've dunked mine underwater in a sink before just to test it. It holds well. I've been meaning to drive over it with my car to confirm it's strong as well. haha.
Also, the otter box that Heir offers (the same box i bought on Amazon) can hold my RSA Predator, LOD, and customs without any problems. When I had the Headstage Arrow, I was able to store that and my ipod touch in it as well.