Williams is trying to make the four-man New Zealand Under-17 team to contest this year's world championships, while the Baldwin brothers and Atkinson are in the mix to make the team to compete at the Asian Australasian and Oceanic Championships, in Korea during August.
Both representative teams will be selected after the nationals.
Some of those competing this weekend are using the two-day event as a last chance to qualify for nationals, which the Northland region hosts every five years, Northland Regional Waterski Association president Glen Williams said.
This weekend's event also gives competitors the opportunity to familiarise themselves with the lake set-up and where jumps are located, and for judges and officials to see how the technical side of things will operate in a couple of weeks time.
The Kai Iwi Lakes Waterski Club pre-event tournament begins at 7am on both days and concludes at 6pm.