Hello darren,
I'm also from singapore, I'm 19 and was certified as a diver 20 mths ago.
I did my OW in singapore (hantu) and it was an interesting experience! Vis was really really terible. But still, you'll be surprise over the amount of marine life in Singapore waters.
I've done 50+ dives so far in malaysia (tioman, aur, dayang and redang), been to bali twice (saw the mola mola!) and also to phuket and similans last year.
I would encourage you to do the rescue course cause i really enjoyed mine! Leant quite alot from it.
The only barrier i have to diving is the cost. And for teenagers, diving is a costly extravagant sport. (unless your dad's rich) I've spent almost $6000 on it, on equipment, courses and dive trips. Much sacrifice has been made to save money, for the 50 min of compressed air. But its worth every cent!
Its still quite rare for teens in singapore to dive, glad to hear that your parents are willing to let you try what many others deem as a "high risk" adventure.