Without a time machine it’s impossible to see the sort of pristine sea turtle populations recorded centuries ago, says underwater photographer Thomas Peschak – but he’s hoping that his image above “provides just a glimpse of the bounty our seas once held”.

It’s one of four underwater photographs among the 25 images put forward for this year’s Wildlife Photographer of the Year People’s Choice Award. Online voting opens today in the side contest of the Natural History Museum’s annual competition, and continues until 2 February.

The images were shortlisted from more than 49,000 competition entries from across the world.

During Christopher Columbus’s Caribbean voyage of 1494, green turtles were said to be so numerous that his ships almost ran aground on them. Today the species is classified as endangered, but at locations such as Little Farmer’s Cay in the Bahamas the turtles can be observed with ease.

An ecotourism project run by fishermen, some of whom once hunted turtles, uses shellfish scraps to attract them to the dock, as shown in Peschak’s “Turtle Time Machine”.

Other underwater images to look out for on the NHM voting site include Andrey Shpatak’s “Eye to Eye”, which depicts a Japanese warbonnet fish; “Drawn and Quartered” by Laurent Ballesta, showing grey reef sharks feasting on grouper at Fakarava Atoll in French Polynesia; and Sam Sloss’s Lembeh coconut-octopus shot “Shut the Front Door”.

The Natural History Museum in London reopens on 3 December, and the People’s Choice Award winner will join the existing 100 images in its Wildlife Photographer of the Year exhibition, which continues until 4 July next year. The top five People’s Choice images will also be displayed online.

Wildlife Photographer of the Year is developed and produced by the NHM and the 57th competition is currently open for entries.

Divers wishing to enter can do so here but should note that they have only until 11.30am on Thursday, 10 December to do so.