The turquoise waters of the Tara River run for over 140 kilometres through the pristine mountains of Montenegro, which are home to the deepest river canyon in Europe.
The Tara River Canyon, which stretches to a length of 82 kilometres and is 1300 metres at its deepest, is best navigated through an adventurous rafting tour.
"Go right! Go right! That's it, now everyone together," screams tour guide Nenad Neso in a mix of Serbo-Croat and English as he attempts to steer the boat through the roaring waters and away from the rugged rocks.
Six people paddle furiously through the rapids as their gasps are drowned out by the crashing water all around them.
The Tara cuts through the mountains at this point not far from the Croatian coast like a knife, making the canyon the second deepest in the world after the Grand Canyon in the United States.
Time and again the churning waters throw the boat forward into the air before it lands with full force back on the surface, while the occupants are soaked to the skin and already sit knee-deep in water.
Everyone continues to paddle, making sure that their feet are positioned firmly under the straps attached to the boat's bottom so as not to lose balance. Fortunately, the rapids are negotiated quickly and soon the river is calm once again, allowing everyone the chance to catch their breath.
The members of the all-male tour group are equipped with neoprene wetsuits, red protective helmets and life jackets.
The friends from Moscow and Montenegro set out early in the morning from the mountain village of Kolasin to experience three days of adventurous rafting through Montenegro into neighbouring Bosnia-Herzegovina.
The Tara River is located between the mountains of Bjelasnica, Sinjajevina, Ljubisnja and Durmitor.
It emerges from the confluence of the Opasnica and Verusa Rivers in the Prokletije mountain near the border with Albania and winds its way through valleys and wild forests before mixing with the Piva River on the border with Bosnia.
There are only a few steep routes down to the river's bank, meaning it can only really be explored by boat.
Most travel agencies in Montenegro offer the opportunity of rafting down the Tara in one, two or three day packages. Business is brisk along the stony banks of the Tara in Splaviste where the tours mostly begin.
"Everyone lends a hand," says Miki, who has been organising rafting tours for 13 years, as he begins taking the dinghy down from the roof of his SUV.
"The first few kilometres have lots of rapids and rocks so plenty of paddling will be necessary," he explains.
The canyon becomes calmer and broader further on before becoming particularly dangerous on the final 15km before the border with Bosnia.
"It's possible for beginners to go rafting on the river in summer but in spring and autumn, rafting on the Tara is really only something for professionals and adrenalin junkies," says Miki.
Large amounts of melt-water and rainwater are the reason for the roaring rapids along the Tara, the perfect time for Miki to train his team and show them some rafting fun.
Nenad Neso is one of the best around and without him the six-man group wouldn't have a hope of successfully negotiating the Tara in their boat.
The boat goes around in circles and sometimes comes perilously close to rocks whenever the team fails to paddle at the tempo demanded by Neso.
Departure point for the rafting tour is the Vila Jelka boarding house, which 32-year-old Miki runs together with his father in Kolasin, a sleepy village that can be reached in two hours by car from the Montenegrin capital Podgorica.
Kolasin has barely been touched by tourism as most visitors to the country head straight for Montenegro's Adriatic coast.
Locals call Montenegro "Crna Gora", which translates as "black mountain". The highest peaks are snow-capped, while lower down the slopes are covered by lush, green forest.
The smell of grilling meat permeates the clear mountain air but the smell of burning plastic also assaults the senses because, unfortunately, fly-tipping is common throughout Montenegro.
However, the authorities are working hard to tackle the problem.
Montenegro, which only became an independent state in 2006, hopes to become the first ecological nation in the world and has enshrined the protection of the environment and natural habitats in its constitution.
"Turning our country into a location for eco-tourism is the future for Montenegro," says Miki.
Further information: See visit-montenegro.com.