its used as in somebody is getting loose, its a Victorian (Australian) hockey slang used to describe somebody who is uncontrollable/abusive/loose/loud while under the consuming of dangerous amounts of alcohol

the whale tail is the shape formed when a g-string rides up high over a womans trousers

an individual who disregards all social norms and behaviours that are considered by the majority to be acceptable, respectable or appropriate; while demonstrating an exceptional tolerance to alcohol consumption and educating the masses on the numerous and unique ways that the C-Bomb can be inserted into a conversation