In my opinion, you'd better not wear contact lenses when you are swimming. The reasons are as follows:
First, As we know, the water in the swimming pool are not clean. If the water immersed into your eyes while your wear contact lenses, It will cause infection to your eyes.
Second, if the contact lenses are off, they are difficult to find, and if you don't have extra glasses, you are a high degree of myopia, it will be very dangerous.
Well, you'd better not to wear contact lenses when you are swimming, because the pool of water generally contains a lot of chlorine hypochlorous acid and other substances and it may bring some discomfort to the eyes, or it will cause eye injury and infection. I heard a piece of new that a girl got blindness because she wears contact lenses during swimming and got terrible eye infection. That's terrible. I do hope you should not wear contacts. Well, do not worry. You can wear prescription swimming goggles to make you see clearly.
Maybe you could, but don't do that. There are a large number of microorganisms in water when you are swimming or diving. It's easy for your eyes to get infection or irritation. Hence, the eye risk would associate with the health risk. However, you could use some ways to avoid the contact lenses touch the water directly, if you have to wear the contact lenses in water. Firstly, the protective goggle is the most effective way to protect your contact lenses in water. It could prevent microorganisms from outside and keep your contact lenses in the right place when you encounter waves or water splashes. Or you should choose soft and disposable contact lenses, which has larger circumference to firmly stick to your eyes, and it could decrease the water pressure to your eyes.