Tactics reminiscent of the early American frontier days are now being used in Vietnam. Lieutenant Commander Donald D. Sheppard, UBN, of Coronado, California, aims a flaming arrow at a bamboo hut concealing a fortified Viet Cong bunker on the banks of the Bassac River, Vietnam on December 8, 1967. (Photo by AP Photo)

A member of the “Bloco Ultima Hora” group gets off a boat during Carnival of the Waters, where costumed and colorful boats navigate the river Tentem, around the islands near the city of Cameta, Brazil on February 8, 2018. (Photo by Ueslei Marcelino/Reuters)

An aerial view shows a Russian Troika, a sledge drawn by three horses, competing on the ice-covered Yenisei River during the annual Ice Derby amateur horse race near the Siberian settlement of Novosyolovo, south of Krasnoyarsk, Russia March 17, 2018. (Photo by Ilya Naymushin/Reuters)

A Sadhu or a Hindu holy man stands on the banks of the river Ganges before taking a holy dip during “Kumbh Mela”, or the Pitcher Festival, in Prayagraj, previously known as Allahabad, India, February 3, 2019. (Photo by Adnan Abidi/Reuters)

A mock-up of a typical British suburban home is seen sinking into the River Thames, in a protest by Extinction Rebellion to demand faster government action on climate change in London, Britain on November 10, 2019. (Photo by Extinction Rebellion/Handout via Reuters)

An Indian boy sells flowers to Hindu devotees of Lord Shiva as they perform rituals after collecting water from the river Ganges during the holy month of Shravan, In Allahabad on July 22, 2019. Shravan is considered the holiest month in the Hindu calendar with many religious festivals and ceremonies. (Photo by Sanjay Kanojia/AFP Photo)

Long-tailed mayflies (Palingenia longicauda) at Tisza river near Tiszainoka 135km (84 miles) southeast of Budapest, June 23, 2013. Millions of these short-lived mayflies engage in a frantic rush to mate and reproduce before they perish in just a few hours during “Tiszaviragzas” or Tisza blooming season from late spring to early summer every year. (Photo by Laszlo Balogh/Reuters)

“Hydrocynus goliath, also known as the goliath tigerfish, giant tigerfish or mbenga, is a very large African predatory freshwater fish. The giant tigerfish is restricted to the Zaire River system, Lualaba River, Lake Upemba and Lake Tanganyika”. (Photo by Tigerfishcamp / Tourettefishing / Bigfishesoftheworld)