Is this equivalent to answering a question by saying you have so much of something you are swimming in it? In English if I was a farmer and had an amazing harvest someone could ask me "How many turnips do you have?!" and I could respond "Dude, I'm swimming in Turnips" or "I'm swimming in them".
So we learned during these lessons that flying creatures drink beer and germans swim in milk! What a strange world!! What I really learned here is that "in the milk" seems not be a correct english translation, however I would prefer harder german excercises than these nonsense sentences!