I wish I could help you more, but this is all we have. We just got back into camping with a new motorhome a couple weeks ago. In the eighty's we had a boat also and spent most of our time at the Colorado River. Now the kids are grown and it's just my wife and our Golden Retriever.
We made our first trip in the new motorhome to a campground called "Echo Lodge". http://www.echolodgeresort.com/
We went there often when we had the boat. You can back right down to the river with a sandy beach. Their rules are dogs must be on a leash at all times. We had the leash and also a 20' leash to stake to the ground. We didn't need it! I'm personally one who follows rules, however it's pretty "kick back" here. Our camping neighbor had two German Shepherds and all our dog's played and retrieved off leash in the river.
Unless they specify no dog's at all, I think you can just evaluate each situation and enviroment and make a decision from there. We will be traveling alot now with our dog and I'll post if we find anything good.
Have fun and good luck!