Superheroes can appear in many disguises – but in north Norfolk this weekend they were clad in wetsuits and goggles for a coastal adventure which raised a record-breaking £40,000 for a children's charity.

The annual Norfolk Superhero challenge pitted 170 determined competitors against some of the county's most beautiful scenery, centred around the coastal village of Burnham Overy Staithe.

In bright midsummer sunshine, the quadrathlon began with a one-mile open water swim from Gun Hill followed by a gruelling four-mile kayak through the harbour.

Cheered on by enthusiastic crowds of onlookers lining the creeks and the quays, the superheroes took to the road for the 48-mile cycling leg before an eight-mile run across sand, tracks and mud flats – ending with an energy-sapping slog across the marshes.

The racers competed in pairs, with the winners Dave Walker and Niall McCallum completing the course in 4hrs 15mins.

But the biggest round of applause was saved for the pair who finished last: Peter Pugh, 71, and David Brooksbank, 68. The competition's oldest team battled their way to the finish line after nine hours, claiming the wooden spoon and the 'Spirit of Superhero' award for encapsulating the ethos of the event.

Sophie Ellis, who co-organises the event with Jess Lapping, said: 'These two came in as we were halfway through the presentation, so we stopped the ceremony and got everybody out of the marquee to form a funnel for them as they came out of the creek.

'It was really emotional. They set themselves a challenge which seemed impossible, but they achieved it through gritting their teeth and making a lot of jokes along the way. And they also raised the most money for charity – over £6,500.

'It was a great day. We had a later start this year, so there were a lot of people on the beach in the sunshine and it made it a fantastic day for both spectators and competitors.'

After his team's success, Mr Brooksbank wrote to the organisers, saying: 'The more I think about the amazing reception we got at the finish, the awards and the whole event, the more emotional I become.'

So far, the event has raised £40,000 for Nelson's Journey, a Norwich-based charity dedicated to supporting bereaved children and young people throughout Norfolk.

Colin Lang, the charity's chief executive, said: 'I was very pleased to attend the Superheroes event at Burnham Overy Staithe and see the immense willpower of the participants to complete the course.

'Nelson's Journey is so grateful to the organisers who selected us as their charity for the event, and all the participants who have raised us so much money. Many records have been broken over this weekend which includes the largest single amount donated to us from a one day event.

'The money will go a long way in supporting the children on our therapeutic weekends.'

The organisers also thanked the team of more than 40 volunteers who helped to marshall and administer the race.