Now I just had to wonder how the heck it sleeps. at 2 AM...
There is some ocean fish (tuna maybe ? not sure at all) which can't actually "inhale" water and has to move forward to make water go through its gills and breath. It never stops moving, and its "sleep" is more like a low brain-activity period where it keeps moving by reflex, kinda like sleep-walking, or rather, sleep-swimming.