Many factors of price, time and cargo affect the bunker decision and the loadline zones present yet another element to go into the equation. There is nothing new in planning one’s bunkering in order to take full advantage of the zones. There is to this day, an important oil bunkering station at St. Vincent in the Cape Verde Islands which dates back to the days of coal burners. An active market at the time was coal out to the Argentine and grain home and Owners found that they could maximise their cargo liftings by taking just enough bunkers to get them from Cardiff to St. Vincent which is in the tropical area. There they would bunker right down to their tropical marks which was generally enough to last them down to the River Plate and back to Cardiff again. Today’s voyages may be more complex but the principle is the same. Remember also that there is a converse to this where care would have to be taken if a ship were to load right down to her tropical marks at a port on the edge of the tropical zones and then steam, say, due north into a winter zone without having burnt off enough bunkers to bring her up to the winter marks. Even arriving with the winter marks clear may not be enough. Surveyors on Port State Control are not fools and they can easily work out from the ship’s deadweight scale whether or not the ship has nevertheless been sailing through winter zones with the appropriate mark well submerged. This can be a very serious matter and rates far more than a figurative ‘slap on the wrist’ from the surveyor. Not only can the Master find himself facing heavy fines but an overloaded ship is technically unseaworthy and therefore her insurance cover could be in jeopardy.