Sometimes the Player can Breathe in Newly Flowed Water

If a water source is created, and then the blocks below it are destroyed, it lets water flow down like normal. However, if a player's head enters that newly flowed water, their air meter will not deplete (and will replenish if it was not full). Also, the player will be able to break blocks at normal speed, as though there is no water there, even though the water could clearly be seen flowing into that space.