Is Coki Beach the one right next to Coral World? If so, then we have. We grabbed a cab to Coral World right outside the "complex" at the pier for a DIY excursion. There were lots there early in the day. The only issue we had was getting one to go back to the ship, as there was no cab stand there and apparently no way to call one. We ended up taking a shuttle bus that was there for a ship-sponsored excursion, back near the end of the day; I can't remember how we ended up paying for it as we were not part of the group. Perhaps if you know how long you plan to stay you could arrange in advance for the same driver to come back and get you.