I purchased the chart, but more because I enjoy studying nautical charts. If you do your homework and have a sail plan in order you won't really need the chart, but the more information you have the better prepared you are. Our last visit the waypoints were right on and it was very straight forward to the entrance and sighting the "twin sisters". Do heed the advice of shallow water towards the back of the mooring field, it was a low water season on our trip and the last mooring ball available was in that location. We were stuck but only for a second. Do not follow the boats (cats) that cut across the reef, not sure if they have local knowledge of a short cut or they just don't know and got lucky? But I saw several Catamarans approach and leave the anchorage without going through the channel.