Caye Caulker and Ambrgris are both inside the reef and I don't think that there's an appreciable difference except it is shallower in front of Caye Caulker. You never see big sailboats in front of CC, they stay on the leeward side. The land mass is larger on AC, with a spread out populated area about 10 miles long. Caye Calker is smaller and the populated area is 1-1/2 miles long.