"If they've done one event they can try something different.
"They can step up in distance or add a new discipline.
"We try to deliver a top class event."
Mr Gellatly said they were expecting just shy of 1000 participants this year with competitors coming from around the country to take part.
The 50km multisport race takes athletes around the waters of Tikitapu (Blue Lake) and into the Whakarewarewa and Redwood forests.
There is also a 2km under-10 fun run, 5.5km and 10.5km trail runs and walks, a half marathon, a standalone 9km stand-up paddle, 31km mountain bike race and a 42km duathlon.
Mr Gellatly said it would be a great day out for participants and spectators, especially with the premier multisport event drawing some top names.
Races taking place in the Whakarewarewa Forest start at 9am on Sunday, with the multisport events starting at Tikitapu at 10.45am.
Online registrations closed yesterday but people can enter on Saturday from 3pm to 6pm at Holiday Inn.
Details
What: Thermatech 3D Rotorua
When: Sunday, May 31
Where: Tikitapu, Redwoods and the Whakarewarewa Forest
How much: From $20, depending on the event.