Bonito

Rivers & StreamsMato Grosso do Sul,Brazil

Limestone springs in western Brazil so clear you see tens of metres through them, floated down face-first while shoals of fish hold station beside you.

September·Peaking now

Apr–Sep

Winter is the season the whole town works around: the rains have stopped, the springs run clear again and the tracks out to them stay dry. Mornings average 19-21°C while the water holds 23-24°C, so it is warmer in the river than out of it.

Year-round The carbonate-filtered springs hold a steady 23-24°C every month, and their piraputanga shoals are there in any season. What the seasons change is the silt the rains stir in, how full the waterfalls run, and the sunbeam that reaches into the cave in summer.

Bonito is a small town in Mato Grosso do Sul where the way to see a river is to float down it. The outing is called flutuação. In a wetsuit, mask and life vest you slip into a spring-fed stream, tuck your arms in and let the current carry you face down over waving underwater meadows. Shoals of silver piraputanga hold station a hand's width from your mask and refuse to flinch. You can see through this water for tens of metres. That is the local rock at work. Rain sinks into the karst of the Serra da Bodoquena and comes back up in springs still carrying dissolved calcium carbonate, and the carbonate latches onto the silt in the water and drags it down to the riverbed. The same soluble rock is hollowed out below. At Gruta do Lago Azul a cave mouth some forty metres across drops into a chamber holding a deep, still lake. For a few weeks from mid-December the early sun swings far enough round to shine through the opening and light that water an electric blue. A Franco-Brazilian team dived the lake in 1992 and surfaced with the bones of giant sloths and a sabre-toothed cat that died here more than 12,000 years ago. The rivers run clearest from April to September, once the rains stop stirring silt into them. None of this is casual. Biologists set a daily ceiling for every attraction, and municipal law later made those limits binding. The only way in is a dated voucher from an accredited agency — no ticket booths at the rivers, no tour without a guide. That restraint, and the Serra da Bodoquena National Park declared in 2000, is why the water still looks like this.

Worth knowing

Good to know

Every attraction has a fixed daily quota — Rio da Prata and Rio Sucuri fill first, and the vouchers exist only through accredited agencies, never at the river itself.
Take the first float of the morning — the light reaches the riverbed without glare, nobody upstream has stirred the sediment yet, and you share the river with far fewer people.
Sunscreen and repellent are banned in the springs — they would film the water everything here depends on. The wetsuit the operator issues is your sun cover instead.
Even inside the dry season one heavy storm can cloud a river for a day or two — put the float early in your trip so there is a spare day to move it to.
You do not need to be a swimmer — the buoyant wetsuit and life vest hold you up, a guide leads the line, and the current does the rest of the work for you.

Things to do

1
Float the Rio da Prata from its spring
Slip in where the spring wells up and let two kilometres of river carry you, arms tucked in, breathing through a snorkel with your face down. Underwater meadows bend in the current beneath you and the sunlight reaches all the way to the sand — the drift does the moving, so you simply watch.
2
Descend to the blue lake at Gruta do Lago Azul
Some 300 steps drop you through a stalactite-hung chamber to a platform above a lake that reads an impossible blue. From mid-December to mid-January the early-morning sun reaches through the cave mouth and lights the water at its most electric; the rest of the year the blue is deeper and quieter.
3
Walk and swim the travertine cascades
On the Rio Mimoso a forest trail links one waterfall to the next, each pouring over a rounded stone lip built by the water itself: the dissolved limestone that clears the rivers settles out here as travertine. The pools below the steps are cool, faintly milky with carbonate, and you can get straight into them. Stand under a curtain of falling water with the trees closed overhead and the day's snorkelling washes off you.
4
Rope 72 metres down into Abismo Anhumas
A crack in a cattle pasture opens into a shaft, and you go down it on a rope for seventy-two metres in the dark. At the bottom lies a lake with limestone cones nearly twenty metres tall standing in it, half-drowned; you snorkel or dive above them at 18°C.