Hey EdwardMH,
Just some info, if it helps. 1st, in your photo, you have what looks like a german sheppard. You said service dog, they can go and do anything. Many RV parks, have breed restrictions, and they are on the list. I have a border collie, and some even have large dog 40 lbs or less restrictions.
I am also a diver. I have been to a few campground with diving. Mostly quarries or the like. In florida there are some springs that are very clear and 72 degrees year round.
It sometimes is difficult to find a buddy to dive with unless it is a high volume site. Most if not all, will not let you dive alone. I only like warm water areas, which creates the next problem. Hot weather, and your dog is in the RV. Not a good thing at all.
Hope the info helps
Brian