Plymouth gold medallist Ruta Meilutyte will one of the star attractions when Plymouth's waterfront comes alive with sport this weekend.
The Lithuanian 15-year-old is one of four Olympians to take part in the Blue Mile – two days of sport, activities and entertainment which aims to inspire passion for protecting the oceans.
More than 250 people will swim, paddle or stand-up paddleboard around a mile-long course in Plymouth Sound today and tomorrow.
Among them will be 40 members of the prestigious Plymouth Leander swimming club, including Ruta, who won huge support after she powered her way to gold in the women's 500 metre breaststroke. They will swim at 12.30pm today.
She will be joined by fellow Olympic gold winners, slalom canoeists Tim Baillie and Etienne Stott, who will take part in today's kayak event alongside gold medal rower Andrew Triggs-Hodge.
Meanwhile, ocean rower Sarah Outen will take on the "aquatriathlon", meaning she will swim, stand-up paddle and kayak.
Event organiser Conrad Humphreys, a veteran round-the-world sailor, said it was a huge coup to have such talented sports stars taking part. He said: "We want lots of people to come down and cheer on all our participants. the forecast looks great, and it's a highly visible course, so people will see lots of action on the water."
An activities village will provide hands-on displays to engage people with their marine environment, as part of the nationwide event which aims to raise money for WWF. It involves partners including the Plymouth Marine Aquarium and the Marine Conservation Society.
The Blue Mile was first held in Plymouth in 2010, and the city hosts one of the flagship events, but hundreds of "grass roots" sponsored walks and smaller-scale activities are going on up and down the country.
Next week, 450 school children will take part in their own Blue Mile in Plymouth, including education and watersports activities.
The aim is to instil a love of the oceans which will mobilise people to act to protect the marine environment.
Mr Humphreys warned that the world would be facing a "complete catastrophe" if no action was taken. He said: "I wonder what kind of world my two young daughters will be looking at in 50 years' time. Will there be questions about what we did and what we should have done to avoid them being saddled with some really difficult decisions in the future?"