Photographers from around the world are submitting images to National Geographic for the 2017 Nature Photographer of the Year contest. Their shots fall into one of four categories: wildlife, landscapes, underwater and aerials. Here is a sample:
“Ice Cave”

This is one of many ice caves on Olkhon Island, Lake Baikal, in eastern Siberia, Russia. (© Sergey Pesterev/2017 National Geographic Nature Photographer of the Year)
“Swimming over the sleepers”

Divers swim over a pod of sleeping sperm whale in a shot taken in the Caribbean Sea near Dominica. Sperm whales dive as deep as 1,000 meters in search of squid to eat. (© Franco Banfi/2017 National Geographic Nature Photographer of the Year)
“Nature’s fury”

A rotating supercell thunderstorm dances across Kansas farmland. (© Colt Forney/2017 National Geographic Nature Photographer of the Year)
“Weaver and nest”

An African weaver, known for its nest-building techniques, in action. The photographer waited hours to capture the moment. (© Federico Rizzato/2017 National Geographic Nature Photographer of the Year)
“Swimming with salmon”

A man in an Alaskan lake swims through a pool of spawning salmon. (© Brandon Cole/2017 National Geographic Nature Photographer of the Year)
“Porcelain crab”

A porcelain crab peeks out through an anemone as it feeds on drifting plankton. (© Marek Koszorek/2017 National Geographic Nature Photographer of the Year)
“Great gray owl”

A great gray owl on the hunt for rodents in a field in New Hampshire, in the northeastern United States. (© Harry Collins/2017 National Geographic Nature Photographer of the Year)
“Courage”

A lioness faces off against a pack of hyenas in Kenya. After a 30-minute standoff, the lioness got away unscathed. (© Adam Zaff/2017 National Geographic Nature Photographer of the Year)
“Flamingos and their nests”

Flamingos leave their eggs in nests on Tanzania’s Lake Natron, a breeding ground for many flamingos. (© Ge Xiao/2017 National Geographic Nature Photographer of the Year)
“The duel”

Two zebras scuffle near a waterhole in Namibia’s Etosha National Park. (© Sonalini Khetrapal/2017 National Geographic Nature Photographer of the Year)
“Rock pool”

Oblivious to waves crashing about, a swimmer moves through a rock pool near Sydney, Australia, at high tide. (© Todd Kennedy/2017 National Geographic Nature Photographer of the Year)
“Sneeze!”

Galápagos marine iguanas sneeze to expel excess salt water after they feed in the ocean. (© M. Engelmann/2017 National Geographic Nature Photographer of the Year)
“Sword”

A sword-billed hummingbird, in flight in Ecuador. The bird’s rapid movements make it difficult to capture a focused image. (© Sanjeev Bhor/2017 National Geographic Nature Photographer of the Year)
“Drift”

A Pacific man of war navigates close to the beach on a summer morning breeze. Thousands of them wash up on Australia’s east coast every year. (© Matthew Smith/2017 National Geographic Nature Photographer of the Year)
“Volcano”

A view of the erupting Klyuchevskaya Sopka volcano in Russia’s Kamchatka Peninsula. (© Vladimir Voychuk/2017 National Geographic Nature Photographer of the Year)
One first-place winner will be chosen from each of the four categories, and the winning photographs will be published on National Geographic’s website. The grand-prize winner will be chosen from among the category winners and will be announced in December.