700m was a warm up when I swam with the local club in my teens! Today, 30 years on, 700m felt a lot further, and definitely harder. It took about 300m before I really found my rhythm. Swimming helps to regulate breathing, forcing you to be conscious of your breath, to count, to find rhythm and pace, as well as coordinating your whole body. So whilst I was a bit anxious about getting in the pool again, remembering just to breathe, kick, pull, count, repeat, eventually I relaxed into it.