Index: src/water_map.h
===================================================================
--- src/water_map.h	(revision 27212)
+++ src/water_map.h	(working copy)
@@ -16,25 +16,26 @@
 #include "tile_map.h"
 
 /**
- * Bit field layout of m5 for water tiles.
+ * Bit field layout for water tiles.
  */
 enum WaterTileTypeBitLayout {
-	WBL_TYPE_BEGIN        = 4,   ///< Start of the 'type' bitfield.
-	WBL_TYPE_COUNT        = 4,   ///< Length of the 'type' bitfield.
+	WBL_TYPE_BEGIN        = 4,   ///< First bit for the structure kind, in m5 bitfield.
+	WBL_TYPE_COUNT        = 4,   ///< Number of bits, for the structure kind, in m5 bitfield.
 
-	WBL_TYPE_NORMAL       = 0x0, ///< Clear water or coast ('type' bitfield).
-	WBL_TYPE_LOCK         = 0x1, ///< Lock ('type' bitfield).
-	WBL_TYPE_DEPOT        = 0x8, ///< Depot ('type' bitfield).
+	WBL_TYPE_NORMAL       = 0x0, ///< Clear water or coast, in m5 (structure kind bitfield).
+	WBL_TYPE_LOCK         = 0x1, ///< Lock, in m5 (structure kind bitfield).
+	WBL_TYPE_DEPOT        = 0x8, ///< Depot, in m5 (structure kind bitfield).
 
-	WBL_COAST_FLAG        = 0,   ///< Flag for coast.
+	WBL_COAST_FLAG        = 0,   ///< Flag for coast, in m5.
+	WBL_RIVER_FLAG        = 0,   ///< Flag for canal on river, in m6.
 
-	WBL_LOCK_ORIENT_BEGIN = 0,   ///< Start of lock orientiation bitfield.
-	WBL_LOCK_ORIENT_COUNT = 2,   ///< Length of lock orientiation bitfield.
-	WBL_LOCK_PART_BEGIN   = 2,   ///< Start of lock part bitfield.
-	WBL_LOCK_PART_COUNT   = 2,   ///< Length of lock part bitfield.
+	WBL_LOCK_ORIENT_BEGIN = 0,   ///< Start of lock orientiation, in m5 bitfield.
+	WBL_LOCK_ORIENT_COUNT = 2,   ///< Length of lock orientiation, in m5 bitfield.
+	WBL_LOCK_PART_BEGIN   = 2,   ///< Start of lock part, in m5 bitfield.
+	WBL_LOCK_PART_COUNT   = 2,   ///< Length of lock part, in m5 bitfield.
 
-	WBL_DEPOT_PART        = 0,   ///< Depot part flag.
-	WBL_DEPOT_AXIS        = 1,   ///< Depot axis flag.
+	WBL_DEPOT_PART        = 0,   ///< Depot part flag, in m5.
+	WBL_DEPOT_AXIS        = 1,   ///< Depot axis flag, in m5.
 };
 
 /** Available water tile types. */