Abismo Anhumas

Useful Information

Location:	23 km from Bonito. (-21.145062, -56.600196)
Open:	All year daily. [2020]
Fee:	Contemplação: , Flutuação: . Mergulho até 18 metros: . [2020]
Classification:	Karst cave river cave
Light:	provided
Dimension:
Guided tours:
Photography:	allowed, prior authorization for tripod required
Accessibility:	no, physical fitness required
Bibliography:	Heros Augusto, Heros Lobo, Edvaldo Moretti (2009): Tourism in Caves and the Conservation of the Speleological Heritage: The Case of Serra da Bodoquena (Mato Grosso do Sul State, Brazil), Acta Carsologica. 38. 265-276. 10.3986/ac.v38i2-3.127. researchgate
Address:	Abismo Anhumas, Centro de Treinamento, R. General Osório, 681 - Centro, Bonito 79290-000, Tel: +55-67-3255-3313. E-mail:
As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then. Please check rates and details directly with the companies in question if you need more recent info.

History

1970	cave discovered unintentionally after a forest fire.
1999	opened to the public.
2019	35º Congresso Brasileiro de Espeleologia (35º CBE) held in Bonito.

Description

Abismo Anhumas (Anhumas Abyss) is a mostly waterfilled cave with a vertical shaft to the surface. When you are on the surface its what the name says: a dark abyss with deep water on the bottom. The cave is not developed, at least not as a show cave, nevertheless it is very popular. It is a diving hotspot and while it is very popular the requirements to enter it are physical fitness, scuba diving experience, and some effort. That's why we classified it not as a show cave.

The organization which manages the site installed a sort of lift for divers, a steel rope which lowers the divers down to the water level. Here at a depth of 72 m is a floating deck from which the dive starts. As always with such dangerous extreme sports venues, security is the most important factor. The situation itself is quite demanding, but the equipment is checked intensively to avoid failures of any kind.

The lake is estimated to have 24,000 m³ and is up to 80 m deep. The water level changes with the outside weather. It is actually the groundwater level and when the groundwater is replenished during the rainy season it rises, and during the dry season if falls. The visibility is very good, around 60 m.

The cave has numerous large stalactites and stalagmites. 20 huge stalagmites are submerged in the lake, obviously they were formed while this part of the cave was not submerged. The highest stalagmite is 20 m high. Around noon the sun shines through the abyss on the cave lake and illuminates the underwater speleothems with a blue glow.

There are actually three options. It is possible to make a scuba dive in the lake, to snorkel and float on the surface, or to make a boat ride in a gum boat. In all three cases its a two day event. On the first day you visit the reservation center in the city Bonito to try on the neoprene suit, sign the safety terms. The next day is the drive to the abyss and the actual visit. Wear closed shoes, long trousers, swimwear, and a t-shirt. Bring a backpack with enough water and snack, like energy bars, and a second set of clothes to change afterwards.

At the beginning participants abseiled into the abyss and at the end had to climb back to the surface using SRT. For this reason there was a training session in both techniques the day before, that's why the reservation center was originally called training center. A few years ago an electric winch was installed which effortless lowers and raises the participants in five minutes.