human
This will show you, said the expert,
gpt
Wash a tunnel out?
human
That's what they do. You know how you can bore a hole in a sand-bank, don't you, with a stream of water? Well, it's just the same with a mud-bank down below, only you need more pressure. Sometimes we use a stream of compressed air. The diver steers the hose just as a fireman steers the fire-hose, and once in a while gets knocked over by the force of it, just as a fireman does.