It's an awful big continent isn't it? I mean, like a lot of people live there. For swimming purposes, however, there are really only two countries you need to know about: China and Japan (and Tae Hwan Park of South Korea). India, despite a population north of 1 billion, seems to still be limited to athletic dominance in cricket and pole gymnastics, neither of which will be contested in London (wherefore art thou Virdhawal Khade?). But both China and Japan will field strong teams. Unless you want to default to the usual American response of "I am ignorant and can't process very foreign names and therefore will pretend this person came out of nowhere when they've actually been internationally relevant for quite some time", I suggest you brush up on the below.
Sun Yang: The second most default response for any Chinese swimmer is to go "I don't believe this result, they are definitely cheating/on drugs amiright???". Yang is a prime candidate for both default responses because he's young enough to not have been a factor in '08 (the last time people payed attention to swimming) and he's so dang fast. Impress your friends by talking about what a great closer Yang is. Say things like "Did you see that last 50 in Shanghai?" or comment on his size (1.98m tall, or 6'6 for those metrically disinclined). Bonus points if you mention he is trained by Denis Cotterell aka Grant Hackett's coach. If they ask about Grant Hackett? Definitely dig a little deeper than "sleeping pill guy".
Park Tae-hwan: Ah, good old Tae Hwan. You'll have an easier time since Park became an international star in his mid teens like Michael Phelps. According to Wikipedia, his nickname is "Marine Boy", so use that as you will. Also, someone more talented than me might want to take the following image and run wild with some memes. Just sayin:
If you've already set your friends up on Sun Yang, now it's time to play devil's advocate with yourself and say that you totally think Park is taking the 400. Ignore their confusion as to why you are arguing with yourself. If you were alive during the cold war, feel free to root for Park over Yang in a symbolic, ideological battle for American style democracy over oppressive communism like Stallone-Drago in Rocky IV.
Takeshi Matsuda: This guy rocks at getting impressively beat by Michael Phelps in the 200 fly! Speaking of...
Ryosuke Irie: Never fails to delight swim nerds with world class in season backstroke racing. Never fails to disappoint by not going any faster at international meets. We're really picking up the pace here:
Kosuke Kitajima: Ah, I knew we would find a compelling Japanese swimmer somewhere. Kitajima swims for history in London, and remains a hugely polarizing figure among american swimming fans . Greatest breaststroker of all time? Probably. Dirty rotten cheater? Possible, but when you consider the context of breaststroke, a stroke that we either need to officiate with underwater cameras or give up completely on regulating, it becomes less clear. If Kitajima wins, you can impress your company by guaranteeing ahead of time that he will yell like a complete maniac at the conclusion of the race.
Anastasia Zueva: What's that you say? Russia should have been included in the Europe preview? The ghost of Genghis Khan vehemently disagrees (or possibly I forgot about them kinda sorta). Zueva is one of the most likely "Franklin-slayers" the rare swimmer who could touch just ahead of Franklin if she's at her best. She's been among the world's best for quite some time so a top result wouldn't be surprising from her, although Russia's track record with senior swimmers is pretty abysmal at the moment.
Satomi Suzuki: You can forgive yourself a little "where did she come from?" with Suzuki only because Japan has more world class swimmers in her favored event (200 breast) than anyone in the world. In a hypothetical, aggregated 800 breaststroke relay, Japan would defeat the US by .18 seconds. Ummmm, and that's really important to know.
Jiao Liuyang: What's that? Tom, get away from the computer! Serious- twroineornlaladlkklass
TOM DUKE HERE. DO NOT CHEER FOR ANY CHINESE SWIMMER IT IS IMPOSSIBLE THAT THEY COULD DO WELL WITHOUT CHEATING. ALL CHINESE SWIMMERS SHOULD BE CONSIDERED GUILTY UNTIL PROVEN INNOCENT. WATCH THE 200 FLY WITH IMMENSE SHAME IF EITHER JIAO OR ONE OF HER TEAMMATES WHO IS DEFINITELY ALSO CHEATING WINS. DUKE OUT.