I would say pretty close to 0%.

Dolphins in most cases shy away from humans. With the amount of people around at this time of year they are not often seen. The best chances to see dolphins will be just inside the reef during the mornings. They usually swim south about 200-300 feet offshore along the island while feeding. I see them on a regular basis while driving to work. Also in the bay behind the island or behind Caye Caulker. Unless you spend alot of time in the water (tours) you will most likely not see any. Sorry.