Learning to swim in the Amazon river basin also means learning to avoid flesh-eating piranhas and snapping caimans.
Residents of the Mamiraua and Amana Sustainable Development Reserves, deep in the Amazon rainforest, are experts at the art of survival. But they're just as at home caring for local plants and animals.
Life here is a balancing act: you learn to avoid dangerous creatures, harvest the jungle fruit, and go with the flow as the seasons change and the river rises and falls.
Roads are scarce -- and in many areas, non-existent -- so the rivers serve as highways, affected only by the changing water level.
Some riverside homes jut into the water on a raft or logs that allow them to float if the tide rises. Other homes are built on stilts for protection from high tides.
The main source of income for Amana reserve residents is harvesting acai.
The purple fruit, known scientifically as Euterpe oleracea, looks like a dark grape and is popular in Brazil. Nutrient-dense and antioxidant-rich, it is increasingly popular in health stores in the United States and Europe.
"Here we have plenty of acai," said Joao, 52, who lives in the village of Boa Esperanca. "But today we've picked enough."
Harvesters, usually children, climb up acai trees -- which look like coconut palms but have a thinner trunk -- to break off the long drooping branches packed with rows of berries.
It's a risky aerial feat some 20 meters (65 feet) above ground. To train, the children practice on shorter trees.
- Monster fish, bald monkeys -
The rainforest also provides locals with the extraordinary pirarucu fish, also known as paiche or arapaima (scientific name: Arapaima gigas).
This can weigh up to 200 kilos (440 pounds) and grow to three meters (10 feet) long. It is coveted for its tasty meat but vulnerable to overexploitation.
The Mamiraua Institute wants fishing to be carefully controlled and local residents, who recognize the fish as an important source of income, set quotas.
But that close relationship with surrounding fauna is not always what scientists of the Mamiraua Institute would like to see.
Dona Maria, 71, has taken home a baby bald uakari monkey (Cacajao calvus) -- a symbol of the reserve and a legally protected species.
The red-faced primate is known for its coat of long fur that sharply contrasts with its bald head and bright red face.
"For me, it's like a little dog. We found it in the jungle and it's always in my arms," says the woman, who happily cuddles the monkey.
- What World Cup? -
Usually, the silence in Sao Raimundo do Jaraua, a riverside village of some 20 homes, is interrupted only by the gentle splash of river dolphins emerging for air, or the cawing of an unseen bird.
The rest of Brazil -- Latin America's economic powerhouse with huge mega-cities like Rio de Janeiro and Sao Paulo -- might as well be on a different planet.
During the World Cup in June, one village family invited scientists with the World Wildlife Fund-Brazil and the Mamiraua Institute to watch Neymar and the rest of the team battle away in Russia. The television was powered by a diesel generator.
But neighbors appeared indifferent to the fate of the national team.
One family chatted, ignoring the action, while two children rowed out on the river and a group of young people showed up exhausted after a day of fishing.