Brazil
To look less like a gringo don’t take a towel to the beach, buy a sarong or kanga - sold everywhere for two or three pounds. Also avoid changing on the beach as wriggling into or out of your cossie attracts looks of incredulity from Brazilians. Although the girls are happy to wear “dental floss” bikinis, going topless will attract lots of unwanted attention.
If you want to join in a game of football on the beach, just ask. Most guys will be happy to oblige and, given the language barrier in Brazil, it’s a good way of going native. They’ll probably make monkey of you, but if you score a goal, you’ll have a fantastic story to bore your mates with back home.
Do all this on Ipanema-Leblon - Copacobana is about as cool as Eastbourne.
I am not sure if it's actually illegal but it's certainly frowned upon. You can wear what you like, as small as you like, as long as there is something there preserving your modesty, even if very little is left to the imagination. As I understood, from good carioca (people from Rio) friends, it's very 'low class' to be topless and have a 100% tan. That's something for the ladies of the night...
There's a fantastic bikini shop in Ipanema called Bum Bum! Best beach wear ever! Not recommended for anyone over a size 12 however - the sizes are tiny. Rio's beaches are pretty posey so it's good to fit in.
Ipanema
I've noticed that tourists, especially from the UK, opt for black T-shirts (in 35C heat!), trekker-style sandals and top of the range shoulder bags: local people don't wear/use these. The shoulder bags in particular are a 'green for go' sign for muggers. Look at what the locals are wearing and follow suit - be invisible. Beach wear: be absolutely minimalist - swim wear & flipflops ONLY.
anywhere
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