The most efficient solution for me was to hire a car with the driver, and combine the visit to Nanxun with another of the nearby water towns. In order to overcome the language barrier - for those for whom it exists, like me! - best was to let the concierge hotel negotiate with the driver. They can also help plan the trips around water towns more efficiently - i.e., tell you which two are best visited on the same day. I had a trip of 6 water towns arranged like that over 3 days.
You can also take an organised tour.
From Shanghai, its ca. 125km drive - take the highway to Huzhou.