Similar case happened on MS River on Gassoway Lake. This was an oxbow lake cutoff from the main river until the water was up high enough to get into it. People were arrested for fishing it. Long story short, the judge ruled that even though the water was navigable, the land underneath was private and the only thing that was allowable was navigation (no hunting no fishing). The law of navigable waterways does NOT include hunting/fishing rights, the land is still privately owned. However, the regulations were put there to allow fishermen to moor and hang nets to dry from these areas but not hunt/fish.
This may be a similar case to yours, but not sure. IF the pond was private and then connected to the main river, its still private
I understand your frustration, believe me, but they are likely in the right here, just as many (not all) of the landowners in SE LA. People think that because the place is open water, that they should be able to fish/hunt there, and I was once in this camp. However, since the land is subsiding so much, what was land is now underwater, their land is still there, so technically they own it. If the state just 'took' all that land and made it public, then for some godly act the land reappeared, the landowner just lost his land. I understand both sides, I was mad at CCA, but then I realized that they were probably not going to win the fight and need to focus on coastal conservation and fixing the problem of land disappearing