I'm really really interested in learning to dive (most aspects really, but scuba on reefs is an interest of mine - I'm really into natural history and marine biology so it's something I've wanted to do for a while). I'm physically fit (run twice a week, good volleyball and soccer player, very low body fat, not particularly strong though, don't do weights or anything and I'm quite skinny), and have good commitment to things I'm interested in BUT - I'm not a very strong swimmer. I'd say I'm decidedly below average at surface swimming - I know what to do, but I always find myself getting tired after a pathetic amount of swimming, and chlorine plays fuck with my eyes so I don't swim underwater in the pool. If it was necessaryI can't imagine I could manage much more than 500m, absolute tops, without stopping for a break, and I haven't done more than about 100m in one go for years. I also swim probably once or twice a year, tops, always on holiday.

Is this a massive problem and something I have to overcome before I take some scuba lessons? What sort of swimming standard do I need to achieve and is it a problem that my underwater swimming is basically non-existent due to the chlorine problem? Would it be easier for me to take some diving lessons and actually put my finances and effort into that, rather than wasting my time swimming lengths in an indoor pool (which I find boring anyway)? Is the buoyancy and movements underwater totally different to surface swimming? I reiterate that I'm above average fitness and am prepared to work out/work.

The bouyance and movements under water are totally different.
It is not about fitness, you will most certainly be well above what is needed.
And the swimming technique is totally different under water, you just paddle with your fins. And you do not even need to swim fast or far, you just paddle around looking at the reefs.

I say just go for diving directly. You'll love it!

You know you can wear goggles in a public pool, right?