Nunui monofin is consired a start monofin. The feet are secured by putting the feet into 2 big footpockets. The ‘socks’ fits around the ankle to secure the fin.
The nunui monofin provided straps for a better fit. I recommend against use those. If you are in a situation you don’t feel safe these will make it harder to kick your fin off.
Want to upgrade? Tails made for the Nunui monofin will also fit the Linden Monofin