The way the SSI system works is after your Open Water Dive Course you would have between 4 - 6 logged dives, do a couple off course dives and then look at doing a couple of specialty diving courses ie Deep, Navigation, Night, or Boat etc. Once you have completed two specialties (all diving specialty courses require the academics and 2 dives except Deep which is 4 dives) and logged 12 dives you are then are certified as a specialty diver, here in Australia if you can produce the 2 certification cards for the specialty courses SSI will issue you a free Specialty Diver Certification card with the 2 specialties printed on the back. Do a few more dives and 2 more specialty courses and when you have logged your 24 dives have it verified by your local SSI dive store and you will be issued your Advanced Open Water diver cert card free of charge ( here in Australia, not sure about the rest of the world). Master SCUBA Diver requires that you be an Advanced Open Water Diver, complete a Stress Rescue Diver course and have logged 50 dives, and then get it verified by the SSI Dive Shop to get the free of charge Master SCUBA Diver cert card. this comes under the recognition through experience motto of SSI and the SSI Total Dive Log System helps you keep track of your progress as you log your dives and do specialty courses.
SSI's equivalent cert level to PADI,s Advanced Open Water Diver, is the Advanced Adventurer and is conducted in a similar fashion, you get to learn about five different specialties and do one dive for each specialty, these are just to give you a taste so you can make a more informed decision on what specialty courses you would like to pursue.
However most dive shops recommend the specialty courses that they can easily run in their area. The chances of a dive shop in a tropical location offering the Dry Suit specialty are fairly slim or if the dive shop dives a local wreck frequently you can be sure that Wreck Diver would be on offer. Wildcat Dive in Caloundra Queensland Australia strongly recommends Deep and Navigation and highly recommends Night and Boat. Deep well because its Deep Navigation so you feel more comfortable knowing you can find your way home, Night because you can dive 24hrs a day not restricted to just sun up to sun down and well Boat because your already diving from a boat.