The geology of the western Black Sea region lends itself to the formation of caves and canyons. Water that collects behind the Bolu and Ilgaz plateaux carves its way through the Kastamonu and Zonguldak regions. The process takes millions of years and creates caves which eventually turn into canyons as the water tries to reach the sea. The Kizilelma cave that we recently featured in Atlas will one day also become a canyon. With a drop of 100 meters (330 ft.) in 4 kilometers (2.5 mi.), the Sehriban canyon was an irresistable challenge.

We first learned about Sehirban canyon in Kumköy where we were staying as guests. A farmer living near the field where we had set up camp approached us and asked us if we were working for the dam project. When we became acquainted, he insisted that we accompany him to his house and be his guests. That's when he told us about Sehriban. He also told us that the Devrekani Canyon, through which the Atlas crew had recently passed, was less challenging than this one. Our friend was also telling us that there was a waterfall of about 100 meters (330ft.).

Haluk and I were mostly on the boat, with Cemal Gülas following us behind. It was becoming increasing difficult for Cemal to catch up with us and for us to slow the boat down by holding on to rocks and fallen trees. We were flowing downstream, cautiously holding on to our security rope. We decided to stay in the water as long as we could manage it. The biggest danger was not being able to see through the water. Mud had reduced the visibility so much that we could unwittingly crash into a rock or tree.

It was also difficult to determine whether there were any whirlpools in the dark brown water. We were constantly reminded that one of our friends fell victim to one during the previous trip down Devrekani Canyon. To our horror, we had seen how the security rope was not strong enough to pull him out. The canyon swallowed him despite our efforts and spat him out 30 or 40 meters (100-130 ft.)downstream. He was lucky that the hole out of which he emerged was wide enough for a man to pass through. Given the apparent hazards, we decided to get out of the river before it grew dark.

At one point Cemal Gülas took his water resistant bag and climbed up one of the walls to take pictures. He had taken only a couple when a tree trunk that was flowing downstream hit the boat and began forcing it down the river with Haluk in it. They were gone before we knew what was happening.

Cemal quickly jumped in the water. When I finally caught up with them 2 kilometers down, I saw that Cemal had finally caught the boat. This was the narrowest point of the canyon and they were both forced to take the boat ashore. The turbulent waters were loudly flowing by. The canyon was now definitely too narrow for us to pass through with our boat. As it grew dark, we decided to set up camp.

In the morning, we deflated the boat and returned on foot to the Dagli village. The water was pretty high. We had to wait for it to recede. And it was time for Haluk to return to Ankara. Çagri Gürbüz joined us in his place.

The crew stopped to take pictures when possible. Hakan Yildiz was in the boat when a tree trunk hit it, got tangled in the security rope, and caused the boat to flow downstream into the unknown. The trunk dragged the boat down for approximately two kilometers (1.5 mi.).

The trunk that got entangled in the boat's security rope also ensured our safety by preventing us from being dragged into the very narrow passage downstream (left). The crew had to wait in the Dagli village for four days for the turbulent waters to recede. After the waters calmed down some, we went back to the canyon. The first meters were sunny and enjoyable. As we went by the spot where we were hit by the tree trunk five days ago and reassessed the situation, we realized just how big the danger was (right).

Haluk was able to throw the equipment bag over to the crew. Cemal left Özcan with the rest of the equipment and was rode the flood waters for 2 kilometers behind the raft.

A narrow elbow hides the canyon behind it. The crew checks on the safety equipment as it discusses the best way to proceed (left). The water level had risen significantly after the heavy rain. The crew had to fight the waters (right).

Özcan Yüksek and Çagri Gürbüz, who joined us on our second trip, enjoy the calm ride.

Four days later, we went back to the canyon. This time, the clear blue waters of the Sehriban river were flowing at a leisurely pace. Our mood was lightened by the beauty of the journey up to here. We were soon to see the white foaming waters which forced us to resume a more serious attitude.

The rock walls were now only one meter from each side of the boat. Surrounding us was the foaming water. The only thing we saw when we lifted our heads was a sliver of blue. We were now truly in the canyon. We began to feel the power of the water that had laboriously carved the rock over millions of years and we realized the canyon was no playground.

After the first couple of hundred meters, the canyon turned into a narrow opening. We did not see the waterfalls that our friend in the village told us about, but we did have to jump over rocks that were two to three meters tall. And we had to do this dozens of times. The slippery surface of the rocks presented a problem but what was more dangerous was jumping back into the river. There was a very strong current behind these rocks. We had to be very careful about these "water-stops," which is what they are called in the canyoning jargon.

We tried to jump as far away from these water-stops as possible. If we couldn't, we had to hold on to our bags. They had more floating capacity than our life vests. If we took these precautions, it was almost fun to jump in the water and be dragged downstream.

Once, I could do neither. Cemal, the most experienced among us, was in the back. I was generally the one to lead. At a point where I could not see what was ahead of me, I jumped straight into a water-stop. I was submerged in water and I had let go of my bag. The water that was flowing above me held me down with its octopus-like strength. I could not get my head above water.

Time was flowing outside, but under the water I held my breath, kept still, and almost wished for the water to grow tired. I had made two cardinal mistakes. First, instead of jumping beyond the water-stop, I had jumped right into it. Second, I had unintentionally let go of my bag. Under the water, I could only see foam around me.

At last, the water let go of me, some 30 seconds later. Since I was leading it was my job to encourage the crew. I called out: "It's OK, but jump that way."

We grew tired as we made headway fighting the water and jumping over the many obstacles obstructing our way in the four kilometer long canyon. Since we were travelling in a canyon that was not tried before, the excitement that we were feeling at the beginning of the trip gave way to anxiety and stress. Water is the least managable of all of the elements. It provided us with many surprises. Any one of these surprises, unforgiving of any small mistake, could cost us our lives.

Towards the middle of the canyon, we were halted by a wall that was not yet completely integrated into the canyon. The water formed into a small lake here, flowed through a hole at the bottom, and came out the other side. We did not want to take the risk of proceeding in the water since we did not really know how wide the hole was, or how deep it lay.

The wall was some ten meters (thirty feet) tall. We climbed up using a tree for a ladder. This was the last important obstacle we were to encounter in Sehriban. After a journey that took us eight hours to complete, we reached Kumköy. When we saw children eating cherries up ahead, we were assured that we had travelled the entire length of the canyon. We were the first to ever follow the canyon. Our trophy was an all-you-can-eat feast of cherries.

Beyond the canyon, the water flows calmly to the Black Sea. One member of the crew made it all the way to the sea 10 kilometers (6 mi.) downstream.

Derlitekke, another small river that feeds Sehriban, looked as turbulent as Sehriban after the rain.

The silt that the water piled on the shore sometimes made life difficult for the crew.

Where the Sehriban spreads out on the way to Senpazar.

As we emerged from the canyon Yaylaköy greeted us with the evening sun.