High drama unfolded in a fast-flowing river near Mariental as resident Warren Hanse fought to survive a harrowing ordeal after heavy overnight rains.

Hanse was trapped in his vehicle, which was swept away by the rapidly rising Grundoring River early this morning.

He had gone to assist his brother, who was stuck in another river, but ended up spending nearly 10 hours in the water before being rescued by boat.

Hanse credited his survival to staying calm and praying: "The bakkie got stuck in that hole. It was hanging unbalanced, and the 4x4 could not function. My brother went to get a stronger rope to pull the car back. In the meantime, I didn't notice the water rising. When I looked, it was already there. As it rose, I climbed to the back and sat on the roof. At one point, the water seemed to subside, so I tied a rope to the bakkie's rails and swam to shallower ground, where I waited."

He emphasised keeping calm: "I don't panic quickly. I was very calm, even on the roof, even in the water."

Hanse tried swimming to the riverbank, but the current was too strong. He warned others: "My message is: don't underestimate even the smallest rain. You don't know where it fell, so water might come rushing down. If you get stuck in a little water, leave the car and get out."

A rescue was coordinated by Hardap Governor Riaan McNab, assisted by Mariental Mayor Ethel Isaacks. McNab said, "I contacted officials from the Ministry of Fisheries. We got a boat. It took a while, but by 6am, they rescued him. Luckily, we praise God, no lives were lost. He's our hero, he stood the whole night, almost 9-10 hours in the water, and he was very brave."

After the rescue, Hanse was kept under observation for a few hours at Mariental State Hospital. He expressed gratitude to all who helped save him.