Competitors in last year's Tri-the-Gong bike stage speed past spectators.
More than 2500 triathlon competitors from around Australia are in Wollongong this weekend to swim, cycle and run around town.
The event is the Tri-the-Gong Triathlon Festival, which includes events for most skill levels.
Today's races include the "enticer triathlon", designed as an entry-level event. It comprises a 300-metre swim, a seven-kilometre bike ride and a two-kilometre run (or walk). Competitors can even wear flippers during the swim, but they won't get a medal.
Tomorrow, the serious athletes compete in a range of age groups as well as an Olympic-distance triathlon, which is a Triathlon Australia qualifying race.
This comprises a 1.5-kilometre swim, a 40-kilometre cycle and a 10-kilometre run.
Entries for all events will be accepted on race day.
The weekend's events will involve a range of road closures in and around the North Wollongong area today and tomorrow.
Today, Marine Drive and Cliff Road will be closed from 7.15am to 3pm due to the triathlon events for younger racers, a fun run and an elite relay.
Tomorrow, the triathlon's cycle route will follow Cliff Road to Bourke Street, turning right at Corrimal Street, and then along George Hanley Drive into Squires Way and Carters Lane to Rothery Street.
These roads will be closed to traffic tomorrow from 6.45am to about 2pm, to make way for both the Olympic and sprint triathlons.