Even if you have short hair, some pools will not let you swim without a cap. Beyond that, though, your hair adds a significant amount of friction in the water, so covering with a smooth swim cap will greatly improve your glide and efficiency. When it comes to caps, materials matter. There are a lot of materials to choose from. Latex tears easily and may irritate some people’s skin. Lycra is solid, but it takes a while to dry. Silicone is a great balance. It’s strong, offers great slip through the water, it doesn’t pull your hair, and it even helps insulate your head in a cold pool.