The labor was exhausting and one must wear some clothes because the sun burned one's skin.

They held out until the rising water drove them from the hatch and when they went back to the tug Brown looked thoughtful.
"The men can't keep it up; the thing's impossible! A week like this would knock out the lot," he said.

"We must use native boys and I'm going to get some." In the morning Lister took his first diving lesson, and when the big copper helmet was screwed on and the air began to swell his canvas clothes, he shrank from the experiment.

The load of metal he carried was crushing, he could hardly drag his weighted boots across the deck, and at the top of the ladder he hesitated, watching the bubbles that marked the spot where the diver had vanished.

Then he remembered his promise to Barbara and cautiously went down.
The dazzling sunshine vanished, a wave of misty green closed above the helmet glass, hot compressed air blew about his head, and his ear-drums began to throb.