Gascan and Katori are members of my club, and are a bit preoccupied at the moment, so I'll answer.
In our club (Western Warship Combat Club - a Big Gun club), a shore battery can only be installed to protect a dock, which is located just outside the port of the Axis or Allied fleet. On the dock are vehicles and buildings that ships - usually battleships or cruisers with rotating guns - can shoot off for points. If there is no dock, there can be no shore battery to defend it.
By our latest rules, a shore battery must be a floating shore battery, one foot by one foot, with penetrable sides. It can sink, just like a ship, but it has the thickest balsa armor of any sinkable "vessel" in our club to give it a fighting chance at survival. It can have a pump, just like a ship. In essence, it's an anchored, square hull with a twin or triple-barreled rotating gun, such as the Gneisenau triple-barrel turret used by the Germans as a shore battery in Norway in WWII.
A shore battery is not necessarily that much fun to operate, since it can't maneuver, it's small, and since it's sinkable, it's vulnerable. And if no one attacks the dock targets or the shore battery, there's nothing for the gunner to shoot at, so it can get boring. We don't see them used very often - usually only at special events - because someone has to bring a dock and vehicles to go with them, and they are of very limited value . The only reason we ever see them at the pond is that they add - along with a dock and targets to shoot at - a bit of spice to our games.
Rob