All four went across the second island, over the heather and bracken to where they could see the third island. It lay in the sea before them, like a long blue and brown snake. Beyond they could see one or two more islands.
"Do you really think you can swan so far, Tom?" asked Mary doubtfully, as she looked at the wide spread of water between the second island and the third.
"Of course," said Tom, who wasn't going to give up this adventure for anything. All the same, the distance was further than he had ever swum before.
"Well—good-bye for the present," said Andy to the girls. "We'll get down to the shore here, wade out as far as we can, and then swim. Have you got Tom? field-glasses, Jill? Good—you can watch us through them all the way to the third island!"
The boys went down to the shore, waded into the water, and then, when they were out of their depth, began to swim. Andy was by far the stronger swimmer—but he kept close to Tom, just in case the younger boy got into difficulties.
On and on they swam, using the breast-stroke because Andy said it was the least tiring. When Tom began to pant a little, half-way across, Andy spoke to him.
"Let's do a spot of floating, Tom. That will rest us a little. It's a long way."
The two boys lay on their backs in the water. It was a little rough and choppy, but quite warm. They floated like logs of wood, spread out flat on the water. It was a fine rest for Tom.
Then once more they swam on—but it began to seem as if Tom would not reach the shore of the third island. His arms felt so tired. His legs seemed to have no push in them. He gasped and panted, and Andy began to feel alarmed.
"Tread water a bit," he called to Tom. "Do you think you'll be able to swim the rest of the way?"