Swimming Ability..

It's not important to be a good swimmer as in fast and proficient in various styles, but it's important to be comfortable in the water, imo.

You don't have to be able to win competitions, but you do need to be in control enough not to panic when you are in water over your head. The swimming tests are not timed, and you can use any stroke you like.

if you can swim for 200m then youll have no problem,if you cant may i suggest you get your arse in gear and train a bit ,youll be happy you did when all around you are struggling and youll be the cool one wandering what the problem is.

AS above, if you can float, splash, bob your way to completing the swim test then thats all you need. The rest is about personal comfort. Remember that you essentially have a life jacket on you at all times in the form of your BCD and any wetsuit also asks as a bouyancy device. Are you Irish by any chance?

We have a reputation as brutal simmers!

My problem is with co-ordinating swimming and breating. Basically, I can swim ok so long as I can hold my breath but I can't seem to get the motion right for breathing and can't swim with my head out of the water. Bazarack you're right, I'll probably be fine if I put in some effort practicing before leaving. I really should do so anyway to fully enjoy the areas I'll be visiting.
Yes I'm Irish and I think that's a deserved reputation for an island nation.

Swimming 200m while holding your breath might be a bit difficult... I know that PADI allows you to do a 400m (?) snorkel instead of the normal swimming - are you comfortable with that? But you would still have to do the water-treading skill, which mean you must keep your head out of the water while staying afloat.

300 meters.

But I don't think it is about the PADI norm, it is about: feeling comfortable in the water and not having any problems when you have to swim a bit, or not panicking when you're at the surface and your BCD is not functioning, etc.

So you should be able to 'self rescue'. If you think you're ok with that, fine and go for the 300 meter snorkel, a lot easier than the 200 meter swimming for you. If not, reconsider doing the course.

I agree with you entirely, Steven. I wouldn't recommend anyone to dive unless they feel comfortable in the water and do not rely on "I have a flotation device, so I don't have to swim".

Learn to swim.
Take a class.
It's actually: Relearn to swim as like most (all?) mammals we are born with the instinct to swim. We just forget about it in very early childhood and develop into water induced panic.

It's not just about the diving course. The ability to swim reasonably good can be anything from helpful to life saving for yourself and others.
It's notdifficult to swim and it's lots of fun.