Part of an (otherwise shallow) water having sufficient depth for shipping and designated or customarily used for shipping. The borders of the channel may be defined by natural or artificial banks or by aids to navigation.
Reference: I.H.B. (supplemented)
Please note that this is the term as it stands in the original IALA Dictionary edition (1970-1989)
Centre of buoyancy
International Association of Marine Aids to Navigation and Lighthouse Authorities - AISM