What distinguishes a modified frog kick from a standard frog kick?

In a modified frog kick, the technique relies heavily on the use of the ankles for generating propulsion rather than engaging the entire legs, which is typical of a standard frog kick. This emphasis on the ankles allows for a more streamlined and efficient movement through the water, making it particularly advantageous in a cavern diving scenario where conserving energy and minimizing drag is crucial.

Using the ankles for power enables the diver to maintain better control and positioning in confined spaces or while hovering, which is significant when navigating around obstacles or in areas with reduced visibility. This technique also facilitates the ability to adjust the kick's intensity and direction without the broader sweeping motion that characterizes a standard frog kick. This specific focus on the ankle movement enhances maneuverability and precision, aligning well with the requirements of cavern diving.

The other options don't accurately reflect the primary distinction of a modified frog kick, which centers on the mechanics involving the ankles rather than the entire leg or factors like tempo and ascent.