I see the potential for a small castle at each end of the entrance to the lake, on opposite sides, ala all those small Rhine river Burgs which used to charge taxes to transit as far as they could shoot an arrow from a bow or a cannonball ( from a cannon, of course) , of course then you fell within range of the next little burg and had to dole out some more coin.
Pay twice on the way in, pay twice on the way out, or risk running the channel at night.
SeerBlue