The pool near us had a water walking track around the outside. If you needed help, you could walk with the current. If you wanted maximum exercise, you could walk against the current. Walking near the walls was light exercise, and walking in the center of the track required wearing water shoes, or you'd scrape your feet up against the concrete struggling to move forward. My physical therapist recommended it after a knee injury, and it let me work out far more than I would have been able to if I'd had to support my body weight.