Notothenioids are fish capable of surviving in the sub-zero waters surrounding Antarctica. Equipped with antifreeze proteins for protection, they are benthic, living on the bottom of the sea, feeding on krill and other fish. Many are sit-and-wait predators, moving little with relatively low metabolic rates. A subgroup of the notothenioids, the icefish, are remarkable for being the only adult vertebrates to have lost the oxygen transporting protein haemoglobin. Christina Cheng and Kristin O'Brien tell Journal of Experimental Biology about these extraordinary creatures and how they survive in one of the planet's most inhospitable environments.