World rowing championships medalists Mahe Drysdale and Alan Campbell headline Saturday's 5km Billy Webb Challenge on Whanganui River.
Drysdale was second in the men's single sculls at Lake Karapiro last weekend, while Campbell was third. The race was won by Czech Ondrej Synek.
New Zealand rowing team members Rebecca Scown and Louise Ayling are also schedule to contest the event.
Scown and Juliette Haigh won gold in the women's pairs at Lake Karapiro, while Ayling was second in the women's single sculls to Sweden's Frida Svensson.
It is the third time the event, which marks the centenary of Billy Webb's epic defence of his world sculling title on Whanganui River in 1908, has been held.
A series of single sculls sprints over 500m will be held on Friday, with the winner lining up against as a wildcard entry defending champion Drysdale, Campbell, Duncan Grant, Jon Winter and Robbie Manson in the Billy Webb challenge race.
Ayling and Rebecca Scown will line up against Harriet Austin, Emma Feathery and Ursula Grobler in the women's race.