When is water shallow?

A master of a vessel must at all times know where their vessel is operating. Traditionally this is only thought of in the geographical sense; however, there is a clear necessity, for safe vessel operations, that the master knows where their vessel is in the hydrodynamic sense. This knowledge is also of prime interest to designing naval architects and route planners alike. Water depth has profound effects on vessel performance and to know When is Water Shallow? is the key to successful vessel operation and wash mitigation. The authors propose a series of characterisations to aid the definition of shallow-water and hence provide greater operational understanding. These characterisations cover typical vessel performance indicators such as resistance, propulsion, manoeuvring, etc., but also wash-specific performance indicators such as wave angle, wave decay, soliton occurrence and spectral output.