You might try checking with the county. Here in Douglas County, Alot of the lakes are "parks" and closed to hunting, BUT, I found out there were some ( quite a few actually) with areas of allowed hunting...
I had to talk to a few people to get the info, be presistant(I think the lady that took my call was anti-hunting,) I had to keep calling back until the guy that had the info was actually there. But I got a few more spots to hunt!
I keep a little note book, with names and numbers of people who told me it was ok to hunt, even little maps, and decoy layouts that work. It has come in handy. I had a guy challenge my permission to hunt once, took out my little book, told him who I had talked to, and offered to call and re-confirm. Turned into, "Oh, him, I know him, hows he doing, blah blah blah, I see alot of geese over there, you can hunt there too if you like." So I got his number and name too...LOL!
Also, don't be afftaid to stop by your land use or planning department (my hunting partner works there, so that NICE) and check on ownership. I was surprised how many little marsh areas off the rivers were State Lands owned, or US Lands owned.