More than 1.5 million litres of water is being pumped into ASB Baypark ahead of this weekend's 2015 ENZED Stadium Jetsprints.
Event organiser Matt Minnell said they started to fill the track with water yesterday and would resume today with the aim of having it filled by tonight.
"We're exactly to schedule and it's filling nicely and our concrete start pool is working well," he said.
About 1600cu m of dirt had been removed to form the track and would be replaced with the same amount of water which was equivalent to about 1.6m litres, much of which would be continuously pumped back into the racing channels.
"We've got catchment pits. As the water's splashed out into the drainage system it's pumped back in," Mr Minnell said.
"We can pump 500l a second back into the track."
The big jetboats were capable of displacing 300l of water a second just with their engines as well as what was splashed out.
He was unsure how much water would be used during the competition but said last year it used half the water they expected as very little leaked out of the track into the ground.
"The water table here is very high. Baypark is actually dug into the ground," he said.
"We're definitely very conscious of the water we use and we use it as many times as we possibly can so we don't waste a drop."
Mr Minnell said the water level would be maintained by bore water and topped up from the local supply if it was needed.
The event is in its second year and kicks off on Saturday.
During the two days more than 50 teams from New Zealand and overseas will compete on the course.
Saturday's racing will feature the New Zealand Jetsprint Championships while Sunday will be the inaugural international invitational event where Kiwi drivers will battle it out with those from Australia, the United States and Canada.
Changes to the track this year meant it was not as technical but was wider and faster so would provide the crowd with plenty of excitment.