City of Sydney have Open Days at three of their Olympic pools.
Cook + Phillip Park Pool open day, Saturday 4 November 2017 from 10am to 3pm
Andrew (Boy) Charlton Pool, Saturday 18 November 2017 from 10am to 3pm
Ian Thorpe Aquatic Centre, Saturday 25 November 2017 from 3pm to 9pm
Some of these include free sausage sizzles, face painting, and/or fitness classes.
In practice you can stay from the conclusion of the Open Day activities to pool closing time.
These are the three days a year I am guaranteed a shower. A true tightarse searches all the shower cubicles for a left-over piece of soap.
Make sure you don't give them your real contact details…they will pester you to join afterwards