Rokugan has a vast coastline, and there is a tremendous amount of activity on the sea during the majority of the year. Trade vessels and fishing vessels make their way across the shallow waters along the coast during spring, summer, and fall, and the hardier ships belonging to the Mantis Clan make the long voyage to and from the Islands of Silk and Spice even during the depths of winter.
The Navigation Emphasis can be used to determine your approximate location using the stars, and determine in what direction a specific destination lies (assuming you already know where the destination is and simply want to know where it is relative to you). Navigation can be used on land, but the TN is increased by +10 when doing so. The Knot-work Emphasis is used in working with ropes and cloths aboard a Rokugani sailing vessel.
Note: Mastery Abilites rank 3 and 7 are house rules and are not part of the standard 4th edition ruleset.