You are basically doing a Pull drill. Put this between your legs
Pull Buoy and use these on your hands
Aqua Gloves (not too many laps at first, build up slowly). Maybe after a while add some
Zoomers.
This adds a resistance training aspect to your workout. As odd as it sounds, using the gloves and the zoomers is harder than swimming without them. It's all in the resistance. Be very careful as the gloves WILL put additional stress on your shoulders.