Just spent 10 days at Mayport Naval Base campground - Pelican Roost in Jacksonville, FL. The base has two campgrounds, the other one is Osprey Cove. We loved Pelican Roost - it is on the St Johns River that feeds into the Atlantic Ocean. You can sit at your campsite and watch the ships go by - we saw a cruise ship, tankers, and Navy ships. Beautiful place and we are definitely going back!
Pelican Roost is a limited stay campground - only two weeks; Osprey Cove is for long term. I personally like that Pelican Roost is short-term stay - it allows more people to enjoy this beautiful campground. The staff is very helpful, as is the camp host.