While top–down cascades from fish to phytoplankton have been a core topic in limnology for the past four decades, it has attracted far less interest in marine ecology. This is partly for historical reasons, since lake studies have been motivated by the ability to regulate algal blooms induced by cultural eutrophication, while marine studies have been more oriented towards fish yield and thus bottom–up processes. Also freshwaters are closed ecosystems with lower diversity and complexity, making models and predictions on trophic levels and interactions comparatively simpler. Here, we compare some key properties of freshwater and marine top–down cascades and argue that despite some striking differences, the large number of freshwater studies may pose valuable insights also for marine systems. Moreover, we argue that there is an urgent need for more focus on top–down cascades in marine systems that address how top predators or fishing may propagate through the food web and impact autotrophic biomass, production, C-sequestration and thus ultimately the global carbon cycle and climate.