Rest the mouse cursor on anything in red to see an illustration. Many fish sleep during the day and hunt at night.
Some sharks tend to search for food at night.
There has been controversy for a long time. Many believed that sharks needed to swim in order to breath and hence could not sleep for more than a few minutes at a time. Certain types of sharks, such as the nurse shark and the related rays, have spiracles, organs which force water across their gills, allowing them to stay still and at rest. Sleep is possible for them. Even the other species of shark have been found to sleep when studied.