I reserved a water only site already. But wanting to just sleep in van and not pitch a tent. Has anyone done this? I called park and the person answering said it is ok, although there are no written rules saying whether it is allowed or not.

More power to you! That's not a problem. RV sites have a few more rules, but you should be good in a tent spot.

I do see some people sleep in their vehicles instead of pulling out the tent. I've never seen no written rules about that

Yes, there are no rules as to what you can and can't sleep in at your site.

I have seeing people sleep in their vehicles before instead of having the tent to sleep in the shelters are not that expensive to rent a shelter it's only $30 a night for a shelter but I don't think there's any rules that you cannot sleep in your van so I believe you can sleep in your vehicle there had been times that me and my boyfriend slept in her car after so many hours of camping and being in the water all day we did sleep in our vehicles for a couple of hours I don't think they would be a problem you could call them . I believe it would be okay.