Vampire Bat may not be spawned when player is on water

Vampire Bat may not be spawned when player is on water (this happens when the player is always on boat before the vampire bat's shadow could appear), this is wrong as the vampire bat is flying mobs and thus can cross land-water border:

function Batted:GetSpawnPoint(pt)
    local theta = math.random() * 2 * PI
    local radius = BAT_SPAWN_DIST

	local offset = FindWalkableOffset(pt, theta, math.random()*radius, 12, true) --12

	if offset then
		local pos = pt +offset

		local ground = GetWorld()
	    local tile = GROUND.GRASS
	    if ground and ground.Map then
	        tile = self.inst:GetCurrentTileType(pos:Get())

		    local onWater = ground.Map:IsWater(tile)
		    if not onWater then 
		    	return pos
		    end 
	    end
	end
end