A battleship such as Warspite drew more than ten metres and needed an additional safety margin for unknown shoals and manoeuvring under threat. Commanders would therefore prefer considerably deeper water, pushing its guns farther from the supported troops and targets. Roberts-class monitors drew only a little over four metres and could operate in water around five metres deep. That difference let them carry two 15-inch guns much closer to a beach or even into a river estuary. Shallow-water access was the type's main tactical advantage.
Notable Point · 23:52-25:05
Shallow draught brought 15-inch guns close ashore
Against Warspite's deep draught, the monitor's ability to operate in roughly five metres of water explains its distinctive value in coastal and estuarial operations.