Chapter 4

Tubby was quite sure he’d made a mistake. He wanted to shout back his agreement, but the water choked him. “I’ve made a mistake!” the professor’s voice wailed again. “I’ve been taking _hydrogen_ out of the air instead of oxygen! The water is lighter than ever. You can’t float—you’ll never come up!” The water was black as ink and icy cold, especially at the back of Tubby’s neck. Funny! Why should that be when he was wet all over? He would have to ask the professor that. But how could he, if he were never coming up? …