Should be alright at least up to BullCreek water ski area and Ascot, probably more but haven't been any higher then that and it was like 20+ years ago.
Download the maps and you'll get some idea of how far you can go,
www.transport.wa.gov.au/imarine/Gregory-to-Perth.asp#36360Also if you don't already have one maybe invest in a cheap fishfinder so you'll know the depth you are in , one with a GPS would be a bonus but even something like this
www.bcf.com.au/p/lowrance-hook%C2%B2-4x-fish-finder-bullet-transducer/551789.html?cgid=BCF012505#start=6will give you the water depth.
And if everything else fails remember to carry a long pole with a flat foot when sailing in shallow waters so you can start the outboard and push yourself out of the mud.