In triathlon swimming, your kick won’t necessarily “make your swim stroke” but it will definitely “break it” if you aren’t doing it correctly.  In short, if you DO have a functional kick, it won’t be your primary source of power for a triathlon swim (kicking uses a lot of energy and makes your heart and breath rate go up.  Additionally it wears out your legs you want to save for the bike / run).  However, a dysfunctional kick will throw the rest of your stroke out of whack (and even make you move backwards).  …..Your reward for developing a functional kick for triathlon swimming isn’t necessarily a massive increase in propulsion but it is definitely less drag.  Less drag = going faster with less work. My point? One key component of a functional kick is the ability to point your toes – which requires ankle flexibility. Many of us, runners in particular, struggle with this.  Here is a video from Swimming World Magazine about how to start improving ankle flexibility – its easy to work on in and out of season and although it may be slow to come around, it will make a huge difference in your kick.