Spectators wrapped up against the elements to watch 450 entrants take part in the John Muir Winter Carnival in his home town of Dunbar, East Lothian.
The occasion at Foxlake Adventures centre saw a gruelling cross country event, followed by a wakeboarding session and Cyclocross race around the Hedderwick Hill woodland.
The lake then became the focal point, with an open water winter swim, and the enthralling coastal rowing team drag race.
Local gyms then went head to head with series of Strongman competitions before the day's big finish - the wakeboarding big air competition.
The crowd's enthusiasm took organiser James Barbour by surprise, as the event served to defy the chilling weather.
"This was a hugely-successful event," he said. "We attracted much more people than we thought and the car parks were absolutely bursting at the seams.
"Some may question the wisdom of holding such a large outdoor event at this time of year, but the spirit of it all is to encourage people to get out and about, whatever the weather.
"Conditions might not have been ideal, but we received a lot of positive feedback from visitors, many of whom were delighted that we held such an event at this time of year." Muir was born in Dunbar in 1838, before moving to the United States eleven years later.
Following years of activism, Muir became synonymous with American wildlife preservation and was largely responsible for the establishment of the Yosemite and Sequoia National Parks.
This year represents the 100th anniversary of his death in December 1914.
Mr Barbour added: "We hope the carnival will go a long way in highlighting the life and the work of John Muir, whose name is relatively unknown among Scots.
"In April, there will be an even greater celebration of the man, with the opening of the John Muir Way - a trail which will run from Dunbar to Helensburgh.
"The trail will showcase the types of things John Muir stood for and will hopefully be seen as another West Highland Way."