We took Bradley swimming from around 5 months I think it was. I think the biggest thing you should worry about is keeping him warm. Not so much in the water as hopefully that will be warm anyway, but when you get out, have a nice warm towel ready and dont hang about. We have had no problems with ear infections. We started babyu swim lessons at 6 months, we got taught how to "dunk" them underwater, he has swallowed water before but its never hurt him, he just coughed a bit. Now he loves it, we have to fight to get him out!