I'm really not very fond of Damnoen Saduak market. It's the floating market where all the tour operators go. So, if you are after dozens of boats with all sorts of fruit and vegetables, etc., then this will do the trick, even if it's just photographically speaking. But it's no good for me. For me, it's not a real Thai floating market any more because it's only there for the tourists - it's artificial. Damnoen Saduak no longer has the charm of genuine floating markets, of which there are quite a few in the region...
The only advantage of this market is that it's the only one open all week, but only in the mornings. For a more authentic experience, you need to mix with the local population. I think you should go to the market at Amphawa, which is not far away, or even to the little floating market of Tha Kha.