So, I've been thinking of learning scuba diving.

[Acies]

I have taken the "advanced open water diver" PADI diving license. If I remember correctly there are a few different types of "organizations" which provide licenses. Within each organization there are different types of licenses too. *A google search later* http://en.wikipedia.org/wiki/Scuba_diving - The section titled "Scuba diver training and certification agencies". Suggest you might to read up on that.

I can definately recommend trying out diving, as it is a great experience. It is something I wish to do again, but haven't found my way to (the issues of money & time). The feel is... awesome :]

My best tip(?): Always stay calm. We had a few drop-outs on our course, the main reason was them not being able to stay calm (for example during the removal of the mask and breather while under water).