Keeping a low center of gravity is one of the most important techniques to be a great surfer. You might be excellent at paddling out or have your timing down perfectly when riding waves, but if your stance is incorrect, you can still easily wipe out.
To achieve a low center of gravity, keep your body in a low, crouched position. According to Surfboards Oceanside, you want to make sure that there is "a straight line from the middle of your feet through the top of your head." This means that your neither your head nor your butt should be extended too far out past your feet. It is also important to keep your shoulders forward and pointed in the direction that you are going.
By getting this stance down, you will achieve a low center of gravity, which will ultimately help keep you stable and balanced while surfing. This is important because if a fast wave comes through, it is a lot less likely to knock you off your board if your center of gravity is low. Remaining stable and balanced allows you to pick up speed as well.
Keeping a low center of gravity can also prepare you for your next move. Let's say you want to do a bottom turn for example. Keeping a low center of gravity will help you to do this because it keeps your weight evenly distributed over your board. It also allows you to "extend [your legs] through the turn and power through the turn," according to Surfing Waves.
As you can see, keeping a low center of gravity is the key to becoming successful at surfing. It keeps you from wiping out and allows you to pick up speed and catch some waves.