Sandbars and rocky blooms appear in the Madeira River near Porto Velho, in the Brazilian Amazon, a city enveloped in a dense cloud of smoke from forest fires. Drought is the main cause of the low levels of the river that runs through Porto Velho, which has gone more than two months without significant rainfall. "Most dangerous is the rocky outcropping that is underwater," says passenger Marcio Freitas, "We depend on the Commander, who is in charge and knows the route there and back." IMAGES AND SOUNDBITES