Vietnam’s Son Doong cave, the largest in the world, could hold a 40-story skyscraper inside. The pristine ecosystem has its own river and jungle. Despite its size, Son Doong wasn’t discovered until 1991. It was lost again for nearly two decades and was fully explored for the first time in 2009. (Photo by Jason Speth/HuffPost)

A boy catches a trout while ice fishing on a frozen river during a fishing contest in Hwacheon, South Korea, Saturday, January 14, 2017. The contest is part of an annual ice festival which draws over 1,000,000 visitors every year. (Photo by /Ahn Young-joon/AP Phot)

Naga Sadhus, or Hindu holy men, participate in the procession for taking a dip in the Ganges river during Shahi Snan at “Kumbh Mela”, or the Pitcher Festival, amidst the spread of the coronavirus disease (COVID-19), in Haridwar, India, April 12, 2021. (Photo by Danish Siddiqui/Reuters)

A crustacean walks on a road after flooding went back in Schuld, Germany, Friday, July 16, 2021. Two days before the Ahr river went over the banks after strong rain falls causing severals deaths and hundreds of people missing. (Photo by Michael Probst/AP Photo)

Poisoned River. Abstract Winner. A detailed photograph of a stream filled with poison. “Poisoned Beauty” is a personal project that tells the story of the natural disaster in the Apuseni Mountains in Transylvania, which was a result of chemical waste generated by copper and gold mining, but in a beautifully abstract way. (Photo by Gheorghe Popa/Drone Photography Awards 2021)

A Nepalese woman offers prayers to the setting Sun on the bank of Bagmati River during the Chhath Puja festival in Kathmandu, Nepal, Wednesday, November 10, 2021. During Chhath, an ancient Hindu festival, rituals are performed to thank the Sun God for sustaining life on earth. (Photo by Niranjan Shrestha/AP Photo)

A row of abandoned oil tanks is filled with creepers on the riverside of Liyun River in Huai 'an, East China's Jiangsu Province, May 9, 2023. (Photo credit should read CFOTO/Future Publishing via Getty Images)

Maddie Stanton (L) and River compete in Helen Woodward Animal Center's 18th Annual Surf Dog Surf-A-Thon at Del Mar Dog Beach on September 10, 2023 in Del Mar, California. (Photo by Daniel Knighton/Getty Images)