A 10th anniversary is being marked with a big splash in Auckland today.
The King of the Bays ocean swim marks a decade on the water and today more than 1000 people are taking part.
Event director Scott Rice thinks its success is about the challenge it poses.
"You're out there in an unfamiliar environment and then you get back to the beach and you feel really fantastic. You've put in the training, you've done the event, and it's one of life's kind of little great moments personally for people.''
Mr Rice says around 1100 people are signed up for the challenge, which is by far the most popular of the events.
"And then you'll have sort of 200 in the 1000 metre, possibly about 80 or 100 in the 300, and we usually have about 80 or 100 children in the State Ocean Kids.''
He says eventually people step up to longer distances as their confidence grows.
The flagship event is a 2.8km swim from Milford to Takapuna this morning, while at the other end of the scale there is a 300m `Give It A Go' swim.
There is also a kids' event just after lunch.