The AQWA Jetty is located directly in front of AQWA the West Australian Aquarium.
Stay on Southside Drive when you leave Hepburn Avenue. There will be lots of shops and parking on your right but just ignore them and keep on driving. Southside Drive will turn to the right and then the left and then 'presto', you'll be in front of AQWA.
Parking is not always abundant so you may need to retrace your steps if you can't find a spot. Most of the time you can, and it is free.
Directions to the AQWA Jetty - Hillarys Harbour
The AQWA jetty in about 25 minutes from Perth city by car. Head north on Route 2/Mitchell Freeway and then exit left at Hepburn Avenue. You will cross three roundabouts, the last of which is at the junction of Whitfords Avenue and West Coast Drive.