Jonathan, I'm not sure what you mean when you say you don't know how to swim. That description describes a large range - from folks who absolutely can't swim at all and would risk drowning if they fell into a pool, to others who are poor swimmers but could manage short distances or time periods OK.
I fall into the second category. I'm negatively bouyant (I sink) so surface swimming is hard work, my skills are limited, and as a lifelong cyclist my greatest strength is in my legs, which are of limited help in swimming. Before becoming a diver, I could swim farther and faster underwater, coming up for air at intervals than I could swim on the surface.
However with a snorkel and fins, I can swim forever. Not having to lift my head out to breathe helps with the bouyancy issue, and the fins allow me to fully utilize my leg strength and endurance.
So you may be like me, can't swim but can snorkel, and could dive. But if you fall into the truely unable to swim group, I strongly doubt you'll be comfortable enough in water to snorkel, much less scuba. It isn't that you need to be a great swimmer, but poor swimmers have a greater fear of drowning (rightfully so) and are more likely to panic if a problem arises.
You need to honestly assess your own skills, and consult with a pro before going farther.
