Getting, belatedly, back to the original thread. It's a bit unfair to pick on the K&A as there are idiots in every area (photographed and unphotographed) who pollute the waterways and I really don't believe the description of open sewer is in any case accurate.
I have swum deliberately and accidentally in the K&A on a number of occasions and ingested its water as a result. To date I have suffered no ill effects although I realise that there are ill effects aplenty just waiting to leap out at me. Many locks on the K&A play host to recreational bathersthrough the warmer months so I suppose the more exposure you get to these things the luckier you get - or perhaps it's that phenomenum of built up resistance. My advice to the op would be to avoid falling in to any waterway in future or at least next time keep their mouth shut.
Yes I know there are life threatening nasties in there, but you can't expect rats to pee in a bucket.