People visiting here for the first time are often worried about the beach water “safety” of Mexico. To see official test results for any coastal location in Mexico, by month and year, go to the following link:
http://www.semarnat.gob.mx/informacionambiental/Pages/playas.aspx
And then click on “Elige tu destino turístico.”
A map will be presented on which you can choose the location(s) you want to research.
Details are presented there in table form covering several years.