Hank says, "You have to be ready for this," to which Wu responds, "And by ready you mean off the deep end?" In his answer, Hank mixes metaphors: "There is no shallow end in this pool. This is not something anybody can wrap their head around until they have no choice but to get on board."
To some degree, having those three different descriptions (a pool, wrapping heads around, and a train) indicates the confusion and "other-ness" associated with knowing about the wider world of Grimms and Wesen. There's no simple comparison to be made. Like Hank tells Wu: "You have to get a place where this is a new normal."
