diff --git a/src/p_local.h b/src/p_local.h
index 631920bb6..037e9aa50 100644
--- a/src/p_local.h
+++ b/src/p_local.h
@@ -329,6 +329,7 @@ void P_Attract(mobj_t *source, mobj_t *enemy, boolean nightsgrab);
 mobj_t *P_GetClosestAxis(mobj_t *source);
 
 boolean P_CanRunOnWater(player_t *player, ffloor_t *rover);
+boolean P_CheckSolidFFloorSurface(player_t *player, ffloor_t *rover);
 
 void P_MaceRotate(mobj_t *center, INT32 baserot, INT32 baseprevrot);
 
diff --git a/src/p_map.c b/src/p_map.c
index d0716790b..f78a0b402 100644
--- a/src/p_map.c
+++ b/src/p_map.c
@@ -1848,7 +1848,7 @@ boolean P_CheckPosition(mobj_t *thing, fixed_t x, fixed_t y)
 				continue;
 			}
 
-			if (thing->player && P_CheckSolidLava(rover))
+			if (thing->player && P_CheckSolidFFloorSurface(thing->player, rover))
 				;
 			else if (thing->type == MT_SKIM && (rover->flags & FF_SWIMMABLE))
 				;
diff --git a/src/p_maputl.c b/src/p_maputl.c
index 2e21f5ee3..5acddf09c 100644
--- a/src/p_maputl.c
+++ b/src/p_maputl.c
@@ -730,7 +730,7 @@ void P_LineOpening(line_t *linedef, mobj_t *mobj)
 					if (!(rover->flags & FF_EXISTS))
 						continue;
 
-					if (mobj->player && P_CheckSolidLava(rover))
+					if (mobj->player && P_CheckSolidFFloorSurface(mobj->player, rover))
 						;
 					else if (!((rover->flags & FF_BLOCKPLAYER && mobj->player)
 						|| (rover->flags & FF_BLOCKOTHERS && !mobj->player)))
@@ -772,7 +772,7 @@ void P_LineOpening(line_t *linedef, mobj_t *mobj)
 					if (!(rover->flags & FF_EXISTS))
 						continue;
 
-					if (mobj->player && P_CheckSolidLava(rover))
+					if (mobj->player && P_CheckSolidFFloorSurface(mobj->player, rover))
 						;
 					else if (!((rover->flags & FF_BLOCKPLAYER && mobj->player)
 						|| (rover->flags & FF_BLOCKOTHERS && !mobj->player)))
diff --git a/src/p_mobj.c b/src/p_mobj.c
index 96beed530..6853c06f9 100644
--- a/src/p_mobj.c
+++ b/src/p_mobj.c
@@ -1879,7 +1879,7 @@ void P_AdjustMobjFloorZ_FFloors(mobj_t *mo, sector_t *sector, UINT8 motype)
 		topheight = P_GetFOFTopZ(mo, sector, rover, mo->x, mo->y, NULL);
 		bottomheight = P_GetFOFBottomZ(mo, sector, rover, mo->x, mo->y, NULL);
 
-		if (mo->player && P_CheckSolidLava(rover)) // only the player should stand on lava
+		if (mo->player && P_CheckSolidFFloorSurface(mo->player, rover)) // only the player should stand on lava or run on water
 			;
 		else if (motype != 0 && rover->flags & FF_SWIMMABLE) // "scenery" only
 			continue;
@@ -2940,6 +2940,34 @@ boolean P_SceneryZMovement(mobj_t *mo)
 	return true;
 }
 
+// P_CanRunOnWater
+//
+// Returns true if player can waterrun on the 3D floor
+//
+boolean P_CanRunOnWater(player_t *player, ffloor_t *rover)
+{
+	boolean flip = player->mo->eflags & MFE_VERTICALFLIP;
+	fixed_t topspeed = K_GetKartSpeed(player, false);
+	fixed_t surfaceheight = flip ? player->mo->waterbottom : player->mo->watertop;
+	fixed_t playerbottom = flip ? (player->mo->z + player->mo->height) : player->mo->z;
+	fixed_t clip = flip ? (surfaceheight - playerbottom) : (playerbottom - surfaceheight);
+	fixed_t span = player->mo->watertop - player->mo->waterbottom;
+
+	return
+		clip > -(player->mo->height / 2) &&
+		span > player->mo->height &&
+		player->speed / 3 > abs(player->mo->momz) &&
+		(player->speed > 2 * topspeed || (player->speed >
+					topspeed && K_SlopeResistance(player))) &&
+		(rover->flags & FF_SWIMMABLE);
+}
+
+boolean P_CheckSolidFFloorSurface(player_t *player, ffloor_t *rover)
+{
+	return P_CheckSolidLava(rover) ||
+		P_CanRunOnWater(player, rover);
+}
+
 //
 // P_MobjCheckWater
 //
@@ -2955,6 +2983,7 @@ void P_MobjCheckWater(mobj_t *mobj)
 	ffloor_t *rover;
 	player_t *p = mobj->player; // Will just be null if not a player.
 	fixed_t height = mobj->height;
+	fixed_t halfheight = height / 2;
 	boolean wasgroundpounding = false;
 	fixed_t top2 = P_GetSectorCeilingZAt(sector, mobj->x, mobj->y);
 	fixed_t bot2 = P_GetSectorFloorZAt(sector, mobj->x, mobj->y);
@@ -2985,14 +3014,14 @@ void P_MobjCheckWater(mobj_t *mobj)
 
 		if (mobj->eflags & MFE_VERTICALFLIP)
 		{
-			if (topheight < (thingtop - (height>>1))
-			 || bottomheight > thingtop)
+			if (topheight < (thingtop - halfheight)
+			 || bottomheight > (thingtop + halfheight))
 				continue;
 		}
 		else
 		{
-			if (topheight < mobj->z
-			 || bottomheight > (mobj->z + (height>>1)))
+			if (topheight < (mobj->z - halfheight)
+			 || bottomheight > (mobj->z + halfheight))
 				continue;
 		}