No, I don't think 8 weeks is too early.

I've been taking DS swimming since he was 14 weeks (ie we started 3 weeks ago). It's run by the physio at the hospital. The mums take their bubs in the pool for 15 minutes of "Swimming" which is just us moving them through the water singing along to nursery rhymes. The babies LOVE it. Then after that is done, we get out, change them, feed them and us mums get back in for 45 minutes of aqua aerobics. It's great fun.

The babies can start from 6 weeks and it goes up to 6 months where they then move into proper baby swimming lessons. In our class I think the youngest bub is about 2.5 months. I think it really does get the bubs used to water before they are old enough to develop a fear of it.