The big surprise was that Perth's warmest public swimming pool was the hydrotherapy pool at Bicton Pool, which is actually outdoors. This pool is heated geothermally to a very toasty 35-36 degrees. The pool is small but up to 1.5 metres deep, so it is still big enough to move around in when it is not busy. The main Bicton Pool is primarily reserved for water polo and hence the venue is only open to the public on weekday mornings and for a short window on Saturday afternoon.
The warmest indoor swimming pools in the greater Perth area were the hydrotherapy/program pools at Aqua Jetty, Aqualife Centre, Bayswater Waves, Riverton Leisureplex, Wanneroo Aquamotion, and Fremantle Leisure Centre. All of these pools are maintained at a cosy 34 degrees. Bayswater Waves and Riverton Leisureplex charge you a separate entry price to access the hydrotherapy pools, so if you are planning to defrost in the hydrotherapy pool and then do some laps, it is best to choose one of the other pools listed above.
Beatty Park Leisure Centre - home of the warmest lap pool in Perth (Photograph by Gnangarra...commons.wikimedia.org)
If you are looking to do some lap swimming, the warmest public lap pool in Perth is the 25 metre lap pool at Beatty Park Leisure Centre, which sits at a warm 32 degrees. There is also an indoor leisure pool at this venue that is heated to the same temperature.
The full survey results include the temperature of all indoor public swimming pools in Perth, so you can look up the warmest pool that is nearest to you.