Swim Research Swim Training Floating Fins for Leg Strength and Aquatic Water Exercise &ndash; Swimming Pool Equipment Swimfin Our unique center spine design creates a more structured fin to maximize performance. Long-blade fins are an ideal tool for the development of muscle and technique. Each fin floats in both fresh and salt water, making them easy to retrieve. A tabbed, closed heel provides easy on and off, extra support and comfort. Fins are sized for men, women's sizes are recommended one size down. Full range available in U.S. shoe sizes: Youth 8 to Adult 15.