As a last resort to get to a ball and keep it in play, you can dive for it. Even if you are able to make a successful dive, you still have very low odds of winning the rally. However, successful dives will pressure your opponent into trying more difficult shots, leading to mistakes or skipped shots.
Diving takes lots of practice and is very hard on your body, so if you intend to dive, get a pair of kneepads! In the following video, Ben Croft demonstrates the correct way to dive.