Cancun. Waterproof wallet?

I'm going to Cancun soon and I keep thinking about how I should keep my belongings. I'm thinking I'm going to need to bring a purse or a small backpack to keep all my necessities like water, camera, sunscreen... but then I'm thinking that when I go on my tours like the Isla Mujeres tour where we will get to possibly swim in the ocean, where will I keep my stuff? Are the people trust worthy?
oh yes. and how much would sunblock cost at the wal-mart in cancun??

Take a backpack or whatever, and keep your wallet in a ziplock bag. Maybe use two just to be sure. Take a wallet that you don't care much about too, leave your good ones at home. I would not necessarily trust anyone you don't know. Don't worry about if they are trustworthy or not, as you don't know them so don't take it for granted. I wish I knew how much sunblock was in Cancun! I've never been. Can you not take it on the plane? Why not buy it here? Have fun!!

Yes, take a water proof wallet and don't take anything on the tours that you would be super heartbroken if you lost. Take just enough money for some lunch or some souvenirs, and take a towel and stuff. Never leave your stuff unattended, take it everywhere with you or at least within you eyesight, just like you would anywhere. The sunblock will be about the same price there as it is here. Have fun!!

if u are bringing your wife or something put it in her purse. most girls never get there purse wet or dirty, its there life..