The most basic certification is open water certification followed by advanced open water and then specialty certifications for programs like rescue diver, night diver, photography and such. Most resorts in the Bahamas, Hawaii, the Caribbean offer scuba diving instruction where you can get certified and diving in the same day usually with in hours. However there are PADI certified diving instructors around the U.S. that offer a variety of dive instruction. When I was certified I spent two days in the pool at the YMCA becoming familiar with the equipment and demonstrating basic understanding of the principles involved in scuba diving and then was certified for my open water certification in a lake in Minnesota. My girlfriend at the time was going for her advanced open water so when we took a dive trip to lake Superior we had to get a deep dive in(over 70 ft) and did some structure diving at about 80ft and that is as deep as I have been. AS Diane said check out the PADI website and find a local dive shop. They typically will rent equipment and running training courses year round the only cost being the certification progrma and buying your mask, fins and snorkel.