Spotted some Pilot Boats in the Port of Auckland, New Zealand and Melbourne & Fremantle Australia (Port codes: Auckland:NZ AKL ; Melbourne:AU MEL ; Fremantle:AU FRE).
When a vessel navigates in confined waters, such as in a harbour or narrow channel, it is well known among experienced pilots that the ship handling is greatly affected by the hydrodynamic forces and moments acting between ship and bank or sidewall of the channel.
Tug power has increased considerably over recent decades. Today, some ship handling tugs have a bollard pull of more than 100 tons. In addition, high tug power can be installed in ever smaller compact hulls.