Unco is the Swim Smooth name for this more challenging version of the traditional single-arm drill - so named because it feels really unco-ordinated! Rather than having one arm out in front, your non-stroking arm rests by your side. This means you have to use your balance in the water, core engagement, body rotation and timing, to keep you supported in the water. I'd recommend always wearing training fins unless you want to give the lifeguards a panic attack (joking aside, you'll just get much more benefit from it and it will be a lot less unpleasant!) You are "just" swimming with one arm (sounds so easy!), taking a breath with every stroke and breathing AWAY from that stroking arm. When you first try this drill, you can try breathing to the same side as the stroking arm; this is easier but you'll get more benefit breathing away. The commonest issues I see with swimmers trying to execute this drill are: - Rushing it. If in doubt, slow down. - Not rotating the body both ways. This often goes hand in hand with the first point; you need to swim imagining that you are using both arms, and move your body accordingly - you need time to do this. - Breathing too late, so pausing after hand entry and extension. Instead, you should aim to turn your head as your hand enters and extends - try the cue "follow your shoulder back with your chin". Then, after you take your breath in, at the SAME TIME as you return your head to the water, initiate the catch with the stroking arm and the rotation drive with the OPPOSITE hip. - Try this mantra "Breathe, stroke, breathe, stroke" or Breathe, pull, breathe, pull" You'll likely find that one side is more challenging than the other. If this is the case, when you practise the drill then start with your better side (let it be the teacher), tune in to what feels right, and then try to transfer than to the other side. The best way to use this drill is as a length of drill, followed by a length of swimming, and then repeating on the other side. It's one of those drills that also really improves with a lot of repetition. In time, it will feel a bit less horrible and you'll find that swimming immediately afterwards feels smoother, more rhythmic and like your stroke is more "joined up".