“Hippo Chase”. As we approached the camp the Selinda Reserve of northern Botswana our boat passed by a hippo resting in the water. I turned around to look back at the boat's wake and saw the hippo charging after us! The hippo must've been tired from an all-nighter because he was angry. He rose way up out of the water three times trying to chase our boat! He was coming at us with such force that he created a wake of his own. Photo location: Selinda Reserve of northern Botswana. (Photo and caption by Curtis Simmons/National Geographic Photo Contest)

Students walk to school on the first day of their new school year in Giza, south of Cairo, Egypt September 25, 2016. (Photo by Mohamed Abd El Ghany/Reuters)

People wash in water from a broken water pipeline on the outskirts of Kolkata, India, March 30, 2016. (Photo by Rupak De Chowdhuri/Reuters)

An abandoned tank left by Boko Haram, February 20, 2016, seen on the road to Michika, Nigeria – a town formerly occupied by the insurgents. On April 14, 2014, 300 schoolgirls in the Chibok village in Nigeria were kidnapped by the terrorist group, Boko Haram. Two years later, the majority of these girls are still missing. According to the Global Terrorism Index Report 2015, Boko Haram, which operates mainly in Nigeria, has become the most deadly terrorist group in the world. (Photo by Danielle Villasana)

A saddle-billed stork stands in the grassland at the Nairobi National Park near Nairobi, Kenya January 23, 2017. (Photo by Thomas Mukoya/Reuters)

A villager carries wood while a blackbuck runs on a field near Bhetnoi village in Ganjam District, in the Indian eastearn state of Odisha on May 20, 2018. Villagers of Ganjam district due to their traditional religious belief consider blackbucks as incarnations of Lord Vishnu and harbingers of rain. (Photo by Asit Kumar/AFP Photo)

Deaf and hard of hearing people perform a Buddhist Guanyin Thousand Hand dance to mark Sunday's National Day for Helping the Disabled in Yunnan, Kunming province, China on May 19, 2018. (Photo by Wong Campion/Reuters)

Miss Talavera Bruce 2017, Mayana Rosa Alves, right, takes a cigarette break with two contestants before the start of the 13th annual Miss Talavera Bruce beauty pageant at the penitentiary the pageant is named for, in Rio de Janeiro, Brazil, Tuesday, December 4, 2018. Prison authorities say they organize the annual beauty contest to encourage self-esteem, fight idleness and promote integration among the female inmates. (Photo by Silvia Izquierdo/AP Photo)