We've been a couple of times... 1st time we stayed in Rio Grande & ferried over to the island a couple of different days. Last time we went, we a taxi meet us at the airport, take us down to Ceiba to the little airport there to catch a puddle jumper, & we just stayed on Culebra the whole week. Was fantastic. A little higher since everything has to be booked separate, no "package" deal, but it was one of the most enjoyable times we've ever had.
Culebra, Puerto Rico - The Island Travel Guide here's one link to info on the island. Can't remember what the price was for the little plane, but it wasn't bad, but we had SO much baggage, (took ALL of our scuba gear), we paid quite a bit more than what anyone might normally have to.
Here's another link, probably a better one....
Culebra Puerto Rico Vacation Information
It explains better about the transporation & other things you'll need to know. We stayed at Villa Flamenco Beach, which is right on the famed Flamenco Beach, but there are plenty of little villas or hotels around closer to town you could stay in. We dove w/Culebra Divers w/Walter. He was a little funny (odd) we thought, but thoroughly enjoyed our dives & went out a couple of times w/him. We rented a jeep from Jerry's Jeeps & some days, just ran all over the island, exploring. The snorkeling around there is Amazing! Had Almost as much fun doing that, as we did diving. Melones Beach was especially awesome.
If u stay on the "mainland" & just ferry over or fly over to the island, as soon as the ferry ports, Culebra Divers is right there across the road, facing the ship. There's no time, they'll tell you they'll be watching for the ferry & wait till you walk in, then head off for a dive.
Very laid back.
Good luck in PR & have fun diving!
