I did a similar search late last year and found that all of the tour guides are very expensive. I would either rent a car or use taxis to explore the West (8 mi) side of the island. Stingray City/Sandbar though is a must if you are interested in water activities. I used Soto Cruises for $19/person. We took 22 folks on an excursion with them. It is about 3 hours and includes 3 stops, with the last being Stingray City Sandbar which is waist deep water.