Poison Rivers, lakes, and falls

Think about it, Minecraft has just about every biome and element that other games have like Lava, water, grass, sand, etc. but what about poison? I know they have Poison arrows and potions, but what about poison lakes, rivers, and falls? I think we should add Poison Rivers, Lakes, and falls to the Jungle and swamp biome [and maybe other biomes] to give the jungles and swamps more danger.

The Poison rivers, lakes, and falls would affect the player if they touch the liquid, thus, giving them the poison effect that slowly damages them. You can use a bucket on the Poison water and get a 'Poison Bucket' witch when placed down, will put Poison water on the ground and it will spread around, damaging mobs and/or players [this is also useful for traps]. The Poison river, Lakes, and falls can also be used to fill 'empty bottles' which when using one on the Poison water, you can make 'Poison Potions' [which is useful for other things]