WARNING: HELPING TO CLEAN UP IPANEMA BEACH CAN EXPOSE YOU TO DERISION, HOSTILITY AND AGGRESSION. 

Sunbathing on Ipanema beach on a Saturday and Sunday is no longer a pleasure unless your idea of pleasure is competing for a patch of sand with thousands of others and then lying surrounded by countless plastic cups, plastic bags, biscuit wrappers, beverage cans, plastic straws and even dirty nappies and sanitary towels while your ears are assaulted by the hubbub of beach vendors' cries, other beach-goers' raucous laughter and shouting and blaring music from sound systems.  How people can enjoy sitting on the beach in such conditions, surrounded by garbage and even decorate the sand with their own trash because they are too lazy to throw it in the garbage bins provided is beyond my understanding. 

Perhaps the above is to be expected in this Brave New World of complete environmental blindness and lack of personal and civic responsibility.
However, what you do not expect is to become the object of derision, hostility and aggression if you decide to try and clean up some of the trash yourself. 

Some three weeks ago, I went to the beach on a Saturday with my wife. Just before we left the beach, I decide to remove some of the nearby trash from the sand and waterline. I got an empty plastic ice bag and stuffed trash into it. As I approached the waterline, a group of some 6 or 7 drunken young men demanded insolently and belligerently that I remove their own plastic trash lying at their feet. Realising that they were deliberately provoking me, I responded politely that they could throw their trash in the garbage bins themselves. They insisted and when I refused, I became the target of verbal insults, derision, scorn and hostility. They kicked sand in my eyes and became threatening. I was reluctant to back down but since they were clearly bent on beating me up and I stood little chance of defending myself against a group of drunken yobs, I left the beach quickly with my wife. Needless to say, my wife and I found the whole experience traumatic and have not returned to the beach on a weekend. 
The moral of the story is that some people take pleasure in littering the beach with their muck and trash and resent anyone who tries to clean it up.