When coaching swimming I often talk about imagining you are skewered through the top of your head and out your woo hoo. Your body can then pivot around the skewer. This hopefully gives you the sense of swimming straight and strong without wobbling or crossing over the middle line.
It has been a really interesting exercise this term to play with drills that can help that alignment, specifically at the point in which your hand enters the water. Many people enter infront of their head, their hand then continues to extend outwards towards the end of the pool and makes a wiping action in front of their body. This causes lots of drag and slows the stroke down considerably.
It is impossible to watch what your hands are doing in front of your head and it is only through getting feedback on your stroke and practising your alignment that you can correct this process. Two analogies I like to think of when swimming that help my alignment are making like the number 11 and swimming carrying champagne.
Number 11 – In this instance image you are looking down on your body laying on the surface of the water. Your hands and arms are up above your head making the shape of the number 11. This is the track your hand should follow as you swim, enabling you to avoid crossovers and sneaky table wiping actions as you go. (Taking it even further I imagine my middle finger is like the wire of old school scalectrics and it has to stay on the 11 or it falls of the track, but that may be a bit much for some!)
Champagne – imagine you are carrying a tray of champers on your chest. If you collapse your chest the champagne glasses will all fall and NOBODY likes spilt Champagne. Instead keep your chest proud, shoulder blades together and back and this good posture and form can help you avoid entering the water with number 11 instead of an X or Y!