If you are certified Open Water Diver, the next step would be to do the Advanced Open Water Course, it will allow you to go deeper into the diving specialities.
It takes around 2 days and you plan your learning with your instructor by choosing 5 specialties from a long list of Adventure Dives where Navigation and Deep dive are mandatory.
During the Adventure Dives you will have the option to dive on the best spots in Malta, including shipwrecks, reefs and caves.