Minecraft 14w08a, Minecraft 14w18b, Minecraft 14w19a, Minecraft 14w34d, Minecraft 1.8
Create a volume of water with "/fill ~ ~ ~ ~4 ~4 ~4 water".
Stand underwater and summon a mob using the /summon command. (The bug does not effect spawn eggs.)
The mob will start taking drowning damage immediately, instead of having a "breathing time" as it usually does.
MC-78527 Mobs are summoned with their "Air" tag set to 0