While the skills required for scuba diving may seem difficult for anyone who has never dived before, the reality is that most people can pick up the necessary skills in a short space of time with some theoretical knowledge combined with practise.
A scuba course will typically consist of a fair amount of reading, which will take you through the theory in simple, easy to understand language. You'll be tested on the theory too ensure you have understood it, but your instructor will be on hand to help with anything you have difficulty with.
Of course knowing the theory is one thing, what you really want to learn from a diving course is to actually dive!
After the theory you'll have some knowledge of the equipment you'll
be using, but it isn't until you're actually using it that you'll find
the theory really begins to make sense and stick. Your instructor will
take you through a series of simple tasks that will help you gain familiarity
with your equipment and help you become more confident in the water.
Your first dives are likely to be enclosed - probably in a swimming pool,
but once you've got over this initial stage you'll want to see fish and
the whole underwater world.
You can typically learn to scuba dive in a week with an organisation like PADI or one of the other major diving associations but after you gain your initial qualification - Open Water Diver in the case of PADI - you'll find that your skills improve rapidly just by making dives and after a while you'll almost certainly want to take your diving to the next level.

