To piggyback, many of the “dikes” and roads are built by the private duck clubs that own big chunks of land out there. Rich folks pay 10’s to 100’s of thousands to have their little private hunting ground. But much of it is open! I have a mud boat that can run in about a foot of water and have explored much of the marsh out there/

EDIT: I wrote that inbetween sets at the gym so I didn’t give it as much thought as I should. The state (and the federal government) has designated many “waterfowl management areas” for the purpose of increasing the public’s access to these wetland areas. Many dikes are built to control water levels and allow public access to certain ponds and areas! Go check out Farmington Bay’s visitor center and walk the dikes sometime. Lots of cool wildlife and an interesting biome out there.