I can't see how you can deal with submarines at all.

The beggars can stay under the water as long as they like, they just pop up and show their heads, and if they don't like the look of anything near, down they go again.

I don't see how you can get at them, any way." The young sailor smiled in a somewhat superior manner.
"We've a few ideas left still which the Germans haven't mopped up," he declared.
"Personally," the Admiral observed, joining in the conversation, "I consider the submarine danger the greatest to which this country has yet been exposed.

No one but a nation of pirates, of ferocious and conscienceless huns, could have inaugurated such a campaign." "Good for you, dad!" his son exclaimed.

"They're a rotten lot of beggars, of course, although some of them have behaved rather decently.
There's one thing," he added, sipping his port, "there isn't a job in the world I'd sooner take on than submarine hunting." "Every one to his taste," Granet remarked good-humouredly.