If you mean to experience scuba diving, the answer is it can be done now. You can enroll in a try diving program. Under the supervision and guidance of a dive professional, you can try scuba diving in a safe and controlled environment.
If you had an entry level certification in mind. The first level of accreditation does not take very long. It can be anywhere from 3 to 4 very intensive days as seen in popular holiday spots. Or splitted over several weeks or months if done through small sessions once or twice a week.
If you would like to try scuba diving or earn a certification, you can take a look on the page Scuba diving, where and how to start.