During the winter Narwhals stay in shallower bay areas to feed almost exclusively on benthic fish, which are fish that live at the very bottom of a body of water (in this case, the bottom of the bays). During the Arctic summers they’ll move into open ocean water so their menu increases to include other kinds of fish like cod and halibut.  Narwhals dive as deep as 1,500 metres while fishing, staying underwater for up to 25 minutes. These dives, some of the deepest ever recorded for mammals, can be repeated up to 15 times a day. Since Narwhals don’t have well-developed teeth in their mouths they are thought to suck their prey in and swallow it whole.