Our LO has been in swimming classes for months now, although he didn't start at 6 mos. Maybe closer to 10? So he has been in swimming lessons for 6 months or so.
He really hasn't swallowed that much water, nor has he ever had an ear infection and I question any study linking things like swimming and asthma. I think that link has to do with chlorine and indoor pools, so it is also linked to frequency, duration, ventilation, genetics, air quality, etc....
On the postive side, when he was visiting cousins in the states, he wasn't afraid of the water but his 2+ year old cousin was. Really, ever since we spent a long weekend at Rasa Ria (Kota Kinabalu), he loves the water. He loves the ocean, pools, water slides, bath time and water hoses. Nice to see him having so much fun.