For me, the reason to go to Curacao is shore diving. Not that there is anything wrong with the boat dives, but to me it's kind of like going to a good seafood restaurant and ordering a burger. There are some exceptions such as Watamula.
Plenty of shore diving locations all along the South side from East to West. Google "Curacao shore diving," search "Curacao" here and take a look at the Ocean Encounters, Dive Bus and Curacao Actief websites for more details. You will want a rental car or truck.
Crime? If you leave stuff in your rental truck it will quite possibly be stolen while you are away from the truck. Don't leave anything you care about in the truck and leave it unlocked and you should be fine. Or search "crime" on this ABC islands forum and you can spend hours reading the arguments, theories, causes, solutions, etc.