You usually go to the beach to relax, but on one of Rio's beaches it's a different story entirely.
If you're planning on going to one of Rio's beaches, don't let ANYONE distract you or anyone you are with, because chances are, they're about to steal something from you.
Whether you're on the beach or one of the sidewalk cafes, don't leave your bag unattended, better still don't take a bag at all. But if you really have to, take a nasty looking carrier/shopping bag, so that way they aren't going to think there's anything valuable in there.
The most common way that things get stolen are by thieves in groups. It could be any situation but the idea is the same. One of them will come to distract you, probably trying to sell or asking for something, then while you're looking the other way, their accomplice makes a run for it with your bag. It's very common here, so watch out for it.