George Van Voorn
I don't use the v1.6 rules but in the old v1.4 rules you could move units (and I think it was six then, don't really remember) up to four water hexes in one sea move. The movement starts in a friendly city adjacent to water and ends in a friendly city adjacent to water. You cannot end your move in water. Flyers can also sea move, but again, only a maximum of four hexes and the movement cannot end in a full water hex.
I think that's just it. Oh, and of course you have to watch your stacking limits.
The wife and I are loving this game.
Great, always an opponent around!