Barra de Guaratiba is a surf spot located in Rio de Janeiro. It features a rivermouth break that can deliver some fun waves when the conditions are right. The area can get crowded, and you might run into some localism, so it's good to be aware. The beach stretches for about 40km to the west, but that's mostly military land where access is restricted, though you can paddle or go stand-up paddleboarding without issues.
The surf here is best on a south swell, particularly from the southeast and south, with ideal sizes around 3ft (about 0.9 meters). The waves break over sand and generally offer a left-hand ride. The best time to surf is during low to mid tide with a north-east wind. It's a spot for experienced surfers, as the waves can get fast and hollow, providing barrels on their good days.
You should keep in mind that sharks are often spotted near the rivermouth, so it's something to consider when you're out in the water. Overall, Barra de Guaratiba can serve up some solid waves, but it's essential to be mindful of the local vibe and conditions.