I don't even know what is that which is preventing ships (in this case CD) to shoot their guns when placed close to the shore line, maybe it's depth or coast proximity, maybe both or maybe even something completely unknown to me.
All I know is that ship has to be placed something like 50-70 m of the shore to be able to use guns...Dont ask me why because even much more skilled moders than me have not been able to find the cause or the solution for these issues.
I could also use one even larger platform with radius of something like 140-150 m...
EDIT:
This is very good, objects height editing in Height parameter in data\Terrain\Locations\CustomAreas\MapObjects.ini actually works...