Um, would be helpful if you showed some screenshots of the area. But my best guess would be that the routing is not correct in those areas.
In CAW, if you click "view", "show routing data" and check those areas you may find that the edge of the ocean is just not accessible.
https://imgur.com/Gdsz8UaSo where the red/blue lines are going into the water, a sim should be able to fish there. I'm assuming as I'm no expert with CAW. You don't need to use any non routable paint under the water unless you don't want the sim to go there. (the world I'm showing has not been tested)