There are no changes to the rules, although the 2nd edition rule book includes a Q&A section that the 1st edition does not. The main changes are to the map, only 3 of which are important: 1) Preston is a Port. 2) The London estuary is its own sea square (just divide it into halves following the verticle land borders that are about the right place). Thus a ship in London reaches the English Channel in 2 movement points not 1. 3) There is a single sea square that completely surrounds the tip of Cornwall (Penzeance). Some versions of the first edition map have the tip of Cornwall sitcking off the edge of the map, this caused confusion about whether there was a sea square boundary there. There isn't. They also tried to redo the letters/numbers grid on the map, but it still doesn't match the coords on the cards.