These little grizzly bear cubs had fun making a real splash when their mum took them for a dip to learn how to fish. Kamchatka, Russia. (Photo by Marco Mattiussi/Solent News & Photo Agency)

Lake Baikal is the world's oldest lake, at 25 million years (possibly older), and deepest, averaging 744.4 metres (2,442 ft).

Located in the south of the Russian region of Siberia, between Irkutsk Oblast to the northwest and the Buryat Republic to the southeast, it is the most voluminous freshwater lake in the world, containing roughly 20% of the world's unfrozen surface fresh water.

A Siberian tiger cub is seen at the Hengdaohezi Breeding Center for Felidae on October 26, 2007 in Harbin of Heilongjiang Province, China. Established in 1986, the breeding center is one of the world's largest captive breeding base for Siberian tigers. Distributed throughout northeastern China, far eastern Russia and North Korea, over 400 Siberian tigers exist in the wild, approximately 20 in China. (Photo by China Photos/Getty Images)

Men and Women dressed as zombies walk through Hyde Park on February 25, 2012 in Sydney, Australia. The annual Zombie Walk raises money for the Brain Foundation and this year teamed up with FX channel in promotion of “The Walking Dead” series premiering in Australia this weekend. (Photo by Brendon Thorne/Getty Images)

In this combination image visitors to the London Super Comic Convention dress as their favourite Marvel comic characters at ExCel on February 25, 2012 in London, England. Visitors to the Comic Convention are encouraged to wear a costume of their favourite character. (Photo by Peter Macdiarmid/Getty Images)

Members of Chinese Shaolin Temple Warrior Monks perform martial arts during the “Cultures of China, Festival of Spring” Gala in Toronto, Canada, on February 27, 2016. (Photo by Zou Zheng/Xinhua/Sipa USA)

An actress dressed as Wonder Woman walks between visitors during the season inauguration of the Madrid Warner amusement park in San Martin de Valdeiglesias, near Madrid, Spain, March 18, 2016. (Photo by Andrea Comas/Reuters)

Models pose on Harley-Davidson motorbikes during a media presentation of the 36th Bangkok International Motor Show in Bangkok March 24, 2015. The Bangkok International Motor Show will be held from March 25 to April 5. (Photo by Chaiwat Subprasom/Reuters)