A route within defined limits, surveyed and confirmed to have sufficient depth, designated for use by vessels requiring deep draught.
In practice
IMO routeing measures, including deep-water routes, are published in the IMO publication 'Ships' Routeing' and incorporated into official charts. SOLAS V/10 requires masters to follow adopted routeing measures applicable to their vessel. The master and chief officer must verify before entering a deep-water route that the vessel's draught, including squat effect at the proposed speed, is within the route's charted depth allowance, applying an adequate underkeel clearance margin. Port authority and pilotage area directions may additionally specify the speed and VTS reporting requirements for vessels using deep-water routes in pilotage waters.
Regulatory detail & full definition
A deep-water route is an IMO-adopted shipping route within defined limits that has been hydrographically surveyed and confirmed to have a controlling depth sufficient for vessels requiring a deep underkeel clearance that is not available on the standard navigational track. Deep-water routes are particularly important for very large crude carriers (VLCCs), fully laden bulk carriers, and other deep-draught vessels that cannot safely transit shallower areas of a traffic separation scheme or approach channel.
IMO routeing measures, including deep-water routes, are published in the IMO publication 'Ships' Routeing' and incorporated into official charts. SOLAS V/10 requires masters to follow adopted routeing measures applicable to their vessel. The master and chief officer must verify before entering a deep-water route that the vessel's draught, including squat effect at the proposed speed, is within the route's charted depth allowance, applying an adequate underkeel clearance margin. Port authority and pilotage area directions may additionally specify the speed and VTS reporting requirements for vessels using deep-water routes in pilotage waters.