A photo showing a dead Pacific green sea turtle caught in a piece of fishing line won an award in the Ocean Art Underwater Photo Competition.Abandoned fishing gear is a significant contributor to ocean plastic pollution: 640,000 tons enter the ocean annually.Visit Business Insider's homepage for more stories.The open mouth and empty eyes in the jarring image above belong to a dead Pacific green sea turtle.From the photo, it's not hard to determine its cause of death: A metal hook tied to plastic fishing line remains caught in the turtle's jaw.The image, which photographer Shane Gross took while diving in Eleuthera, Bahamas, recently won an award in the annual Ocean Art Underwater Photo Competition. It took first place in a newly created category: conservation."My dive buddy came to me in tears talking about a poor turtle that was already long dead, tangled in fishing line," Gross wrote in his contest entry. "She didn't have time to remove the line, so she told me where it was and I went back. I didn't want any scavengers to also become entangled. I took my camera because images like this can become warnings for the future."Hundreds of thousands of pounds of fishing gear sit discarded in the oceanpart of a larger epidemic of plastic pollution. According to the National Oceanic and Atmospheric Administration, about 8 million metric tons of plastic enter the ocean annually. Approximately 165 million tons of plastic are currently there already, according to the Ocean Conservancy.Plastic 'ghost gear' can haunt the oceanThousands of photographers across 78 countries submitted their work to the underwater photo contest. Runner-up photos in the conservation category offered other perspectives from the front lines of the plastics crisis: an anglerfish struggling against a dense plastic net, and a reef manta ray attempting to filter feed on plastic particles (below).Gross' image, however, stood out to the judges because of its emotional impact.Plastic pieces in the ocean range in size from microplastics just 1 millimeter across to plastic bottles and straws. All of these bits of garbage can pose dangers to marine life, but large discarded fishing equipment, sometimes called "ghost gear," is particularly deadly.According to a United Nations report, approximately 640,000 tons of ghost gear enters the ocean every year. That's the equivalent of about 50,000 double-decker buses.Researchers have also found that the rate at which sea creatures get tangled in plastic increased 10-fold between 2000 and 2016. Of that total, discarded nets and fishing lines caused 55% of the entanglements; plastic bags caused 10%; and the rest came from nylon, string, and other plastics.Turtles that get trapped in fishing nets often can't get to the surface to breathe, which can lead to them to drown.Green sea turtles like the one in Gross' photograph are listed as endangered by the International Union for Conservation of Nature. In most countries, hunting and killing them are prohibited."We don't want any other turtles, or any creatures, to become doomed to the same unfortunate fate: drowned and wasted thanks to our negligence," Gross wrote.SEE ALSO:32 award-winning underwater photos reveal a troupe of tiny seahorses, a hot-pink sea slug, and fish living in beer bottlesDON'T MISS:The best wildlife photos taken this year reveal a horde of interlocked ants and a vicious stand-off between a fox and a marmotJoin the conversation about this storyNOW WATCH: Why plastic straws suck Click here to read full news..