What if i accidently drink the water at the beach in cancun?

It is never a good idea to swallow sea water, but a little bit won't hurt you. Happens to everyone at times. No, they do not sell " poland springs" bottled water. They do sell plenty of other brands of bottled water everywhere and it is exactly what you should drink. Resorts, hotels often have a purification system, so the water they serve you is fine to drink. If a hotel does not have a purification system, they always give you bottled water.