I got lucky when I stayed at Bahia Honda - typically they are booked 12+ months in advance.  I took a trip to the keys and got to the park super early. They let us know that if we hung out for a few hours and there were cancellations, we could be in line for that spot, but there were 3 other parties in front of us.  Somehow we were able to get a spot on the bayside after waiting, which was great!

I have seen and heard of the beach camping spots at Bahia Honda, but the Bayside was a very pleasant surprise. There were a few cabins and a few tent sites secluded on it's own side, and that's it.  It was beautiful, serene, and everything was perfect.

I keep looking to stay again, preferably on the beach, but every time I go to look there is nothing available even if I push it out a year.  Hopefully I can make it back soon!