diff --git a/src/ship.h b/src/ship.h
--- a/src/ship.h
+++ b/src/ship.h
@@ -20,7 +20,7 @@ void GetShipSpriteSize(EngineID engine, 
  * All ships have this type.
  */
 struct Ship: public SpecializedVehicle<Ship, VEH_SHIP> {
-	TrackBitsByte state;
+	TrackBitsByte state; ///< The "track" the ship is following.
 
 	/** We don't want GCC to zero our struct! It already is zeroed and has an index! */
 	Ship() : SpecializedVehicleBase() {}
@@ -45,6 +45,10 @@ struct Ship: public SpecializedVehicle<S
 	void UpdateCache();
 };
 
+/**
+ * Iterate over all ships.
+ * @param var The variable used for iteration.
+ */
 #define FOR_ALL_SHIPS(var) FOR_ALL_VEHICLES_OF_TYPE(Ship, var)
 
 #endif /* SHIP_H */