There are many great local dive shops that will certify you so that you can gain your open water certification. The two most popular agencies are PADI and SSI, although there are many others throughout the world. If you are from Melbourne, Australia I can highly recommend Bayplay if you opt for PADI, and The Dive Victoria Group for SSI.
Scuba certification cost in Australia will set you back around the $600 dollar mark, although this will vary, depending on which agency and dive store you select. It is important to note that when it comes to your open water certification, don’t stress about 50 dollars here or there. Throughout the rest of the world, prices are comparable although in places such as Asia you may save a few dollars. The most important thing is that you receive the best training with the best advice. After all your initial course will certify you to dive independently.
As I have been trained via the PADI system I will confine my comments to that. Although, from my understanding the various agencies around the world follow similar standards and methodologies.
Although not a complete list, here is a list of the certifications that you can gain via PADI:
Obviously if you don’t plan on becoming an instructor, your course progression would stop at Master scuba diver. The only benefit to achieve this level is really about bragging rights. That being said the rescue diver course was the most enjoyable course I have ever completed.