The waters of the Great Belt are Danish territorial and therefore those using them are subject to Danish law.
This states ‘in internal and external territorial waters there is an obligation for ships to use a pilot if they are:
1) . . carrying oil or have uncleaned cargo tanks that have not been rendered safe with inert air
2) . . carrying chemicals
3) . . carrying gases
4) . . carrying more than 5,000 tons of bunker oil
5) . . carrying highly radioactive material.’
The IMO recommends pilotage from Skagen to Gedser and vice versa for ships with a draught of 11 metres or more following Route T pointing out that the entrances to the Baltic are congested and difficult to navigate.
Between Gedser and Spodsbjerg, the effect of sea level variations caused by a combination of tide and meteorological conditions, together with unknown obstructions on the seabed and sand migration, can decrease the depth to a little as two metres.
Therefore the Danish Pilotage Authority highly recommends that a ship with a draught of 11 metres or more uses the pilotage services established by the coastal State on its passage from Grenaa to Gedser
All ships have the right of ‘innocent passage’ through territorial waters. Innocent passage meaning that the vessel is in constant transit and, short of an emergency situation, will not anchor or call at a port. In addition, ships with a draught of 13 metres or more will be reported to the flag state if they do not take a pilot all the way from Gedser to the Skaw.The increase in draught significantly intensifies the risk of the ship running aground. The Danish Pilotage Authority reports all violations of the IMO recommendation to the flag state. The Tango route is exclusively in Danish waters until the northern section where the safe channels meet international or Swedish waters.