A wetsuit makes you a faster swimmer because a wetsuit gives you buoyancy, lifting you higher in the water, which means you require less energy or force to give you lift (i.e. keep you at the surface) and, more importantly, push you along.
How to swim in a wetsuit
How much buoyancy does your triathlon wetsuit need?
Why am I slower swimming in a wetsuit?
Stronger swimmers will benefit less from a wetsuit than weaker swimmers, as their body position is already better. For weaker, newer swimmers, or less confident athletes, your hips will be level with your head and shoulders rather than below. This should mean that your legs are also at the same level – you might even feel your heels breaking the surface as you kick.
Swimming with a pull buoy in the pool can help mimic the effect of your wetsuit in that it adds that extra buoyancy to keep your body level. That said, we want to be able to benefit from the wetsuit rather than rely on it. Make sure that you practise swimming without a wetsuit too; if it’s hot on race day you might end up with a non-wetsuit swim, which could come as an unwelcome shock to the body!
To get the most out of your wetsuit, make sure you buy one that fits well. You could have the best suit on the market, but if it’s too small/wrong shape it will restrict your movement; if it’s too large it will fill with water and drag.