Tam Coc is a small town approached along a magnificent highway with gates and banners. It must go somewhere else, surely.
The main purpose of Tam Coc is the well-organised tourist trade. After lunch, you are marshalled to small boats rowed (usually) by elderly ladies. Our elderly lady spoke very little English and slightly more French; attempts to communicate resulted in a lot of laughing all round. In the company of dozens of other boats we were rowed up the river, past rice fields and wonderful limestone mountains and through three caves. There is an obvious comparison made with Halong Bay; both are visually delightful.
But be prepared: (1) For high-pressure sales tactics: During the return trip, a plastic box will be produced containing embroidered table-cloths. (2) And for the cold. We should have taken jackets or pullovers and we suffered.