(CNN) — A photo of a river dolphin, or "boto," seemingly posing for the camera at dusk, with the tip of its nose above the water and the sun setting behind it, has won the 2023 Underwater Photographer of the Year competition.
Photographer Kat Zhou, from the US, captured the image in the Amazon, where there is a legend among indigenous communities that the dolphins can transform into handsome men known as "boto encantado" at night, according to a news release earlier this week.
The photo, which beat more than 6,000 images submitted from 72 countries, was hailed by the judges as the best picture they had seen of the species.
"Though I did not witness the transformation, I was enchanted by these beautiful mammals in a different way," Zhou said in the release.
"After seeing how botos would sometimes bring their beaks above water, I wanted a split shot at sunset. Though the water was so dark that I was shooting blind, this dolphin gave me a perfect pose and smile."
The somber image of a humpback whale dying slowly, swimming away from the camera with its tail entangled in ropes and a buoy won the Save Our Seas Foundation Marine Conservation category.
Herrero's photo shows a humpback whale dying of starvation as it unable to swim properly.
Alvaro Herrero/UPY 2023
"Taking this photograph was the saddest moment I've experienced in the ocean," photographer Alvaro Herrero said. "But I am, at least, happy that I could capture this moment and can now share it with the world and hopefully drive some real changes."
Other winners of individual categories include a shot of sting rays gliding over the sandy ocean floor, a whale shark feeding on a school of fish, an elephant's curious trunk underwater, and embryonic fish still attached to their egg sacs, as the photos display the brutality, beauty and sometimes other-worldly nature of marine life.
A selection of the winning and highly commended images can be viewed in the gallery above, while all 130 shortlisted images are available to view on the competition's website.