The PADI System works in modules. Choose the 1st Dive of any of the PADI Speciality Courses to gain a PADI Adventure Diver credit.
Advanced Open Water
Add just two more core dives; deep dive & navigation dive and you gain the PADI Advanced Open Water Certification.
If you really enjoyed a particular type of diving, just add the extra dives required and you will gain a PADI Speciality Certificate.