Surfing New Zealand says 240 competitors are in the national championships in Dunedin which start on Thursday.
It says three of the surfers are ranked in the world top 100.
It is the fourth time the event has been held in Dunedin since it started in 1963 and while there is no prizemoney, the association says there is a lot of prestige in the event.
Heats will be held at St Clair beach with the finals planned for Sunday.
But if the swell gets too big or small, the association says the event may need to be moved up or down the coast.