Read the passage carefully and choose the best answer to each question out of the four alternatives. The instructor's rules were simple. Breathe through your mouth, not your nose; else the mask will fog up. Easier said than done; I got it wrong many a time. But once you fought habit and got the hang of it, the panoramic underwater world revealed itself to you with high-definition clarity. Led by him, I slowly peered through the mask into what till then was crystal-clear water, shimmering in the sunlight. I saw pebbles, sand and my fluid shadow. I was in Nemo's universe. Sea cucumbers, sea anemone, clown fish, star fish, sea horses, parrot fish, butterfly fish and a bevy of colourful salt water fish swam past. A shoal of canary-yellow fish did a merry dance and another with vibrant blue fish followed it. They were oblivious to the snorkelers who struggled to take in the sight of a world so beautiful, so colourful, and resist opening their mouth wide in amazement; the tube would fall off! The writer saw all of the following except: