The shipping lane from Portsmouth Harbour (and Southampton Water) leads from Portsmouth Harbour out past the Nab Tower. It is clearly marked with red and green buoys.
Small boats are allowed to cross shipping lanes but the advice is obvious – don’t hang around in a shipping lane for longer than you need. The ships travel surprisingly quickly, and may have severely limited visibility for some distance in front of them.
Do not enter a shipping lane if you are likely to be becalmed or capsize, and NEVER deliberately sail in front of a ship.
Note that there are special requirements/restrictions in the entrance to Southampton Water because of the establishment of a ‘Precautionary Area’ where large ships turn. Check the chart if you intend to sail through this area.
Point of interest – in our area of the world navigational marks are positioned green to starboard and red to port for entry into a harbour. In the Solent all the marks lead towards Southampton water, so if you sail through the Solent from one end to the other, the buoy colours reverse as you pass Southampton Water.