SDI Open Water Scuba Diver Practice Exam 2025 - Free Scuba Diver Practice Questions and Study Guide

When performing a flutter kick, maintaining straight legs is a crucial technique for efficiency and propulsion in the water. Keeping your knees as straight as possible helps engage the larger muscles of your legs, particularly the quadriceps and hamstrings, while minimizing drag. Flexing your knees can create a more turbulent water flow around your legs, making your movement less efficient and requiring more energy to maintain speed.

A flutter kick should originate from the hips with the legs extended, allowing for a fluid motion that conserves energy and maintains a streamlined position. Although engaging the hips is important, kicking solely from the hips without considering the position of the legs and feet would not facilitate effective propulsion. Using circular motions or allowing your feet to drag can hinder your speed and create unnecessary resistance against the water, leading to fatigue. Therefore, the focus on keeping the knees straight directly contributes to a more effective and efficient flutter kick while scuba diving.