Decisions on measures to improve a flood risk system are in part supported by general ideas about how the system works and should work. After the completion of the Dutch Delta Works around 1990, such new ideas regarding flood risk emerged. Some of these may be appealing at first, but appear debatable after a closer look. In this paper, fourteen such debatable ideas, familiar to most Dutch water professionals, are formulated and criticised, in order to find out what can be learned from them. The most important Dutch national flood risk policy documents since 1990 are reviewed for quotes that illustrate these ideas, complemented by scientific papers and other documents. These quotes present different expressions of these ideas, and their number can suggest whether they are broadly shared or marginal. In twelve of the twenty most important government documents, 47 quotes were found; in 26 documents of other types, another 39. Eleven quotes describe the idea that ‘water should not be our enemy, but our friend’. Fifteen quotes were based on the idea that flood protection entraps us in a dangerous ‘spiral of risk’, which can be stopped, 44 quotes are related to the idea that flood risk reducing measures should be ‘natural’ or ‘move with nature’. The remaining quotes illustrate other debatable ideas, such as ‘water should lead spatial planning’ and ‘rivers should not be squeezed into a corset’. The frequency of such quotes suggests that ideas about ‘water as a friend’, the ‘spiral of risk’ and ‘moving with nature’ have not been marginal. It is however difficult to determine how influential they have been in decision-making, since general ideas are not the only factors leading to decisions. The general critique to the three ideas is that they present preferred measures as generally logical conclusions without a systematic comparison of alternatives for particular situations. Behind the new ideas lies increasing societal interest for objectives like an attractive water landscape (water as a friend), reducing our dependence on technology (spiral of risk) and nature conservation and development (moving with nature). This analysis further suggests a couple of final remarks, which are hard to prove and are open for discussion.