A new book published by the UK Natural History Museum showcases some of the most memorable underwater photographs taken over the last few decades in its annual wildlife photographer of the year competition. Here: Giant gathering by Tony Wu. “The first indication that something extraordinary was going on were the blows, huge numbers of them – the exhalations of huge numbers of whales. Entering the water, the photographer witnessed an extraordinary scene”. (Photo by Tony Wu/Unforgettable Underwater Photography/NHM)

A couple stands next to a poster depicting Dutch politician Geert Wilders and Russian President Vladimir Putin kissing, at a metro station in Amsterdam April 3, 2016. (Photo by Cris Toala Olivares/Reuters)

U.S. Army soldiers with the 1st Battalion, 501st Infantry Regiment deployed to Combat Outpost Sabari, Afghanistan scan their area as they begin a multi-day air assault mission near the Pakistani border of eastern Afghanistan's Khost province May 2, 2012. (Photo by Staff Sgt. Joshua L. DeMotts/U.S. Air Force)

Ghanaian fans take a selfie prior to a Group G football match between Germany and Ghana at the Castelao Stadium in Fortaleza during the 2014 FIFA World Cup on June 21, 2014. (Photo by Patrik Stollarz/AFP Photo)

Magbola Alhadi, 20, and her three children pose for a portrait in Jamam refugee camp in Maban County, South Sudan on August 11th, 2012. Magboola and her family weathered aerial bombing raids for several months, but decided it was time to leave their village of Bofe the night that soldiers arrived and opened fire. With her three children, she travelled for 12 days from Bofe to the town of El Fudj, on the South Sudanese border. The most important thing that Magboola was able to bring with her is the saucepan she holds in this photograph. It wasn't the largest pot that she had in Bofe, but it was small enough she could travel with it, yet big enough to cook sorghum for herself and her three daughters (from left: Aduna Omar, 6, Halima Omar, 4, and Arfa Omar, 2) during their journey. (Photo by Brian Sokol/Panos Pictures)

Strokkur geyser against cloudy sky at sunset. Strokkur is a fountain geyser located in a geothermal area beside the Hvítá River in Iceland in the southwest part of the country, east of Reykjavík. It is one of Iceland's most famous geysers, erupting once every 6–10 minutes. Its usual height is 15–20 m, although it can sometimes erupt up to 40 m high. (Photo by Teatsche Dijkhuis/Getty Images/EyeEm)

TV personalities Kendra Wilkinson and Jessica Hall attend the premiere of STX Entertainment's' “Bad Moms” at Mann Village Theatre on July 26, 2016 in Westwood, California. (Photo by Barry King/Getty Images)

Cave Diver, Anhumas Abyss, Bonito, Brazil: The Anhumas Abyss is an underground cavern with a crystal-clear lake below, more than 260 feet (79 m) deep. A visitor must enter through a narrow opening at the top of the chamber and rappel into the cave. Snorkeling and scuba diving in the lake reveal amazing scenery. Distinctive, conical limestone stalagmites and stalactites occupy the lake and the surrounding area, some reaching 65 feet (20 m) high. (Photo by Marcio Cabral/Nature’s Best Photography Awards 2017)