No we did not have a reservation. We just showed up. I'm honestly not sure how it is on a cruise ship day. I actually messaged them via fb to ask if we could just show up and if there was a cover charge before we left the house and they told us no.
The fans are EVERYWHERE!!! There's no missing them. The whole place is filled with them. I first headed to the left (when facing the water). No, no swimming out...just along the sides by land. I swam a good ways down before turning around (I think there was some buoy's or something to the left) but I seen them everywhere I was. The huge rocks full of coral was to the right, basically right beside the steps leading in. It was so beautiful.
I hope you have a great time! Let me know how it went.