We were there last March Rio Mar Margarittaville. The Bio-Luminescent tours were all booked up but the resort told us it was not recommended at that time anyway due to low Luminescent . I think it depends on the time of year and if a storm has been through the area. Reviews on trip adviser also confirmed. The hike in the Rain Forest is a must. Wanted to go to the caves but did not. Next time. Looks very interesting. If you plan on taking the ferry anywhere get to it very early. Long Long lines to get in.
If you plan on renting kayaks at the resort I suggest reserving that early, they were all reserved the entire time we were there. Jet-ski was way too expensive. Down the road near the kiosks is a public beach with rentals..
It was a nice resort but the area surrounding it looked a bit shady.. Enjoy...