The short answer to this is No. You don’t exactly need how to swim to be able to scuba dive. But it does help to know swim. Since you are trained in swimming, you’d be able to better control the air pressure while diving as you’ll have good control over your breath. You’ll also be able to glide underwater effortlessly. Nonetheless, it doesn’t matter how expert a swimmer you are, if you are a beginner in scuba diving, you still need a guide to help you explore the underwater world. Scuba diving is different from swimming, and you’d need a guide to help you understand the techniques.