You will, as I did, find all kinds of information on the internet about how to swim with the Akumal sea turtles for free and without a guide. Since the 2016 order from the Mexican Government that protects this natural environment there are rules and regulations that apply to the turtle area, including restrictions on the number of daily visitors. Tour operators are required to have a permit to take people out into the protected areas of the bay and if you go it alone you may be breaking the law.