I been diving outside Cancun for 10 years and I only been seeing dangerus sharks a few times, one time I got a little too close when me and my friend were snorkling after 5 pm on the edge of deaper water a Tiger shark show upp and stared too swim around us we had abot 20 meters too the boat and that was nervos meters. We have seen White sharks but not close too shore.
The risk of a shark attack is wery little when you dive and swim in the waters outside of Cancun. My tip is too awoid swimming when its getting dark.