Welcome back to Why Is The Sky. I am Dana Khalil, and today we are going underwater. Lina is nine, she lives in Aqaba right by the Red Sea, and she sent me a voice note asking whether fish sleep, because she has seen them floating very still at night but their eyes are always open. Lina, I did not know the answer, so I did what scientists do when they do not know. I asked someone who does. Dr Sami Khoury studies fish in the Red Sea and he is going to join us by phone to tell us about fish that sleep in bubbles, sharks that rest one half of their brain at a time, and how you can tell a fish is asleep at all. Then I have a challenge for you. You are listening on Witspeak Podcasts.