A tidal wave of interest is building in farming the seas. It’s part of a global rush to exploit oceanic resources that’s been dubbed the “blue acceleration.” Optimistic projections say that smart mariculture – fish farming at sea – could increase ocean fish and shellfish production by 21 million to 44 million metric tons by 2050, a 36%-74% jump from current yields. Other estimates suggest that an ocean aquaculture area the size of Lake Michigan might produce the same amount of seafood as all of the world’s wild-caught fisheries combined. Our work as interdisciplinary researchers studying aquatic food systems shows that these claims exaggerate mariculture’s true potential, and that increasing mariculture in a sustainable way is fraught with challenges. We see freshwater fish farms as a better way to help fight hunger and bolster food security. In our view, governments, funders and scientists should focus on improving aquaculture on land to help meet the United Nation Sustainable Development Goals.