The Catalinas did not take off from Perth Water, they took off from Melville Water, from near the Narrows - and always in a Sth-Westerly direction towards Fremantle.
I agree about them using Melville Water, but
always in a South-Westerly direction? Didn't a Catalina end up "beaching" itself on the Como shore very near the present day Narrows Bridge? Presumably a failed take off in a North Easterly direction? So what happened when an Easterly was blowing?