If you're planning on doing a PADI course but you don't feel like spending your holiday in a classroom you can also do the theoretical part online!
With PADI eLearning you can start right away with your dive theory and work in your own tempo.
PADI keeps adding and improving their online system. Check it out every now and than to see if the're any new courses available.
At the moment all courses are available in English. Open Water Diver Course Online is also available in other languages like Dutch and Spanish.