Which kicks are commonly used when swimming with fins?

The flutter kick and mermaid kick are commonly used when swimming with fins due to their efficiency and effectiveness in propelling a diver through the water. The flutter kick involves alternating leg movements, which provides a smooth and continuous propulsion, making it suitable for divers to maintain speed with minimal effort. It allows for excellent control and direction when underwater.

The mermaid kick, on the other hand, combines a streamlined body position with a fluid, wave-like motion of the legs, mimicking the movement of a mermaid's tail. This kick is particularly useful when maneuvering in tight spaces or when extra agility is needed underwater. It generates propulsion while allowing the diver to maintain a streamlined body position, reducing drag.

In contrast, the side kick and back kick are less commonly associated with the use of fins, as they are not as effective for forward propulsion and energy conservation. The butterfly kick and frog kick are also not as efficient with fins, since they rely more on undulating motions or sweeping motions of the legs, which don't suit the design of fins. Likewise, the crawl kick and dolphin kick focus more on traditional swim techniques than underwater diving propulsion techniques. This highlights why the selected answer is the most appropriate choice for swimming with fins.