Wow! I did the Trek tri and I was joking with my husband afterwards that I was going to end up with some hideous disease after swallowing the lake water - it was pretty gross! I am a very strong swimmer (swam competitively for 10 years, it's the bike and run that I struggle with), so swimming in open water has never bothered me, but it was a little weird to see nothing but brown underwater - that couldn't be healthy. I have been fine since the tri but it is interesting to know that you've had issues.