At the risk of repeating my post from the other day (and a number of other posts in the past), then the rule of thumb is that a watch with a 30m WR rating is NOT designed to be suitable for immersion in water. It's as simple as that, and there are countless articles on the subject on the net, so it's not just a Breitling thing. 50m is the absolute lowest WR rating that I'd personally considering wearing for surface swimming, and if I was diving into the pool or sea, I'd want a minimum of 100m. (And if I scuba dived then 200m is the min). Bear in mind that while it may look more substantial, the Emergency has the exact same WR rating as the Navitimer, and we all know how water-phobic Navis can be.
Obviously there will always be people who will confirm that they have swum in their Emergencys (and Navis) with no problems at all, and that's absolutely fine - I'm not disputing that for a minute. However, I tend to think this is like someone who smokes 60 a day claiming that because they haven't personally suffered a fatal disease, that smoking is perfectly safe to do! Sometimes you're lucky, sometimes you aren't, but the fact is you are increasing the risk of a problem if you are undertaking an activity that you, or in this case your watch, fundamentally isn't designed for.
At the end of the day it's all personal choice what you use your watch for, but if you decide to swim in a 30m WR watch, be prepared for that fact that you may very well have a problem with it as a result, because you are using it for something it's not designed for. Swimming in a 30m watch is kind of like playing Russian roulette with 5 bullets in your revolver! But as the WR rating goes up, so the number of bullets in the gun (and hence the likelihood of "problems") reduces!
