I'm a competitive swimmer and have been doing this for years. I have taught many people my technique and its worked every time. There are a couple steps.

•Have your head as horizontal to the waters surface as possible. This step is critical. I have seen a lot of people attempt ring bubbles horizontally and it never works.

•Slightly stick your tongue out in a pointing manner, like what you would do to a crush you had in elementary. I would say only 3 to 4 centimeters from your lips to the tip of the tongue.

•lastly blow air out softly, not too hard or the circular smooth shape you want will disbursed. Basically you want enough air to where your cheeks fill followed by a gentle force of air.

No one is perfect and it will take a couple tries. If you follow my steps I guarantee you will achieve the perfect ring bubble!