That was Chunky’s broken cage falling into the water off the deck of the ship.
“Look out that Chunky doesn’t fall in!” cried the captain.
Some of the sailors, with ropes in their hands, made a rush, intending to tie Chunky fast to the deck. But they were too late.
[That was Chunky himself falling overboard.] Right into the salty ocean he fell, off the deck of the ship, and then the ship steamed on, leaving the hippo and his floating cage on the big ocean. For the ship had to steam on, or else the big waves would have made her sink.
As for Chunky, as soon as he found himself tossed into the water, he did what he had been taught to do by his mother and father when he was a little baby hippo. He closed his nose and mouth so he would not choke in the water. Fresh water or salt water, did not matter to Chunky. As soon as he jumped in, fell in, or was pushed in, shut went his nose and mouth!
Down, down, down in the ocean sank Chunky. He thought it safest to sink down quite a way at first, until he saw what would happen next. Besides, down under the waves it was quieter than on top, where they were being tossed about by the wind.
Hippos can dive, sink, float or swim as they please, almost like a big fish, but they can not stay under water more than about ten minutes without breathing. After ten minutes they have to come up to fill their lungs with air. Then they can dive again.
So Chunky dived down in the ocean. He did not know how deep it really was, and at first had an idea he might go to the bottom and perhaps find some grass or lily roots there.