Teeming with images of spectacular underwater scenes from around the world, Call of the Blue is the culmination of a five-year project by the photographer and ocean conservationist Philip Hamilton. This groundbreaking book includes contributions from acclaimed scientists and ocean “guardians”, who reveal what drove them to answer the call of the blue. (Photo by Philip Hamilton/The Guardian)

Swans swim over a lake, with the air temperature at about minus 35 degrees Celsius (minus 31 degrees Fahrenheit) as steam ascends above the water during sunset near the village of Urozhainy, Sovetsky district of Altai region, January 26, 2015. About 600 swans annually migrate to the lake, which is heated by warm springs, where they spend their winter being fed by yagers, which helps them to survive the severe cold. (Photo by Andrei Kasprishin/Reuters)

Jellyfish Lake (Palauan: Ongeim'l Tketau, “Fifth Lake”) is a marine lake located on Eil Malk island in Palau. Eil Malk is part of the Rock Islands, a group of small, rocky, mostly uninhabited islands in Palau's Southern Lagoon, between Koror and Peleliu. There are about 70 other marine lakes located throughout the Rock Islands. Jellyfish Lake is one of Palau's most famous dive (snorkeling only) sites. It is notable for the millions of golden jellyfish which migrate horizontally across the lake daily.

Titicaca or Titiqaqa is a large, deep lake in the Andes on the border of Peru and Bolivia. By volume of water, it is the largest lake in South America. Lake Maracaibo has a larger surface area, though some consider it to be a large brackish bay due to its direct connection with the sea.

A general view of the residential area is pictured during dusk at Jodhpur in Rajasthan, April 5, 2015. Jodhpur, also known as the blue city in the desert Indian state of Rajasthan, which residents say originally, was used to show where the highest caste of priestly Hindus live, who wanted to set them apart from the rest of the population. Later the rest of the population followed suit. Another reason for the city to be blue is to keep the buildings cool during the summers, local residents said. (Photo by Adnan Abidi/Reuters)

Boats of fishermen are seen on the dried Poopo lakebed in the Oruro Department, south of La Paz, Bolivia, December 17, 2015. Lake Poopo in Bolivia, the Andean nation's formerly second largest after the famed Titicaca, has dried up entirely. With the water now gone, animals have died off in the millions, according to studies. And the local families, having lost much of their sustenance, have been forced to migrate. (Photo by David Mercado/Reuters)

A large stainless steel shovel lies on top of steamed crabs at the A.E. Phillips & Son Inc. crab picking house on Hooper's Island in Fishing Creek, Maryland August 26, 2015. Workers speed through the lump and back fin meat inside the crabs while leaving the more tedious task of picking the claws to others. (Photo by Jonathan Ernst/Reuters)