Mosquito ditches most likely
There is a reeeaaaalllly long one on the eastern end of Lake Powell, starts a few turns after the marsh ends and you go under the trees and into the creek. About 8 feet wide and you can tell it was cut in. It runs mostly straight and goes at least as far as the power lines to the east of the lake near the fire station on back beach road.
A few years ago after enough big rains to clear some logs and stuff out of there, and the lake was closed to the gulf, I was able to paddle my kayak into the clearing under the power lines!
There was a lot of brush covering the opening on the far eastern side of the power lines so I was unable to go further.
Put in on the northside of bridge to Wild Heron saves the long and sometimes windy paddle from the public boat launch behind Publix. One of my fav paddles in these dune lakes for sure.