Thanks so much for all the replies everyone, I appreciate them and your stories of the neighborhood. I'm still waiting to hear back from whichever authority tells us either way.
It depends on your land title. I live on a lake and my title stipulates the end of my property line is where the water touches the shore. Other’s can have a fixed property line that may not coincide with the water line.
Do you have a copy of your deed? It may come with some special rights.
I recall seeing a real estate ad for a property on Grenadier pond. Appearently it had shoreline rights that allowed them to launch a boat. Maybe that applies to your property too. Then you can really piss the park people off.
I found the ad
https://dailyhive.com/toronto/toronto-home-sale-comes-with-boat-grenadier-pond