Despite our best efforts, there are (still!) many swimming coaches out there teaching swimmers to pause-and-glide when they swim. This is a massive mistake as water is 800 times more dense than air and by pausing in your stroke you instantly decelerate before having to reaccelerate on the next stroke. An incredibly inefficient and ineffective way to swim!
When you watch elite swimmers on TV they can look they are gliding forwards through the water but this is an optical illusion brought about by the length of their strokes. The fact is they achieve that length through good streamlining and a great catch and pull technique, not by gliding.
You should follow the same philosophy in your own swimming, work on your stroke technique by improving your body position, becoming more streamlined and developing a good propulsion technique - transitioning smoothly and continuously from one stroke to the next.
By actively trying to glide you are trying to artificially lengthen the stroke - putting the proverbial cart before the horse.