“out of the depth”の意味は?

名探偵シャーロック・ホームズを現代のイギリスに蘇らせたBBCのテレビドラマ『Sherlock』を観ながら、ETC英会話のトニー先生のレッスンを受けています。

今日はこんなダイアログから。

SHERLOCK:　
I’m a consulting detective. Only one in the world. I invented the job.
JOHN:　
What does that mean?
SHERLOCK:　
It means when the police are out of their depth, which is always, they consult me.
JOHN:　
The police don’t consult amateurs.

さて、the John Watsonと人の名前に定冠詞のtheを付けるのにはどのような意味があるのでしょうか。

Direct translation of “out of the depth” is referring to maybe you are in a swimming pool or the ocean, and you are in water too deep, you can not touch the bottom.
So you have to swim.
You have to make sure you can swim or you would drown.
It would the water will go over your head.
And that means you are out of your personal depth of security.
So but we always use it now for,,,
We will never use it now for swimming.
We always use it for this type of situation, which means if you can not handle your situation, the situation is deeper than your capabilities.
And the water is going over your head.
So you are now out of your depth.
So you need to ask somebody else who can help you.
So in this case, the police can’t think about any solutions, or any ideas of what is happening. which means they reach the maximum depth.
And now they are out of their depth.
They are like swimming round and going, “oh, where can I go? where can I go?”
And Sherlock Holmes is like there, deeper, I am here.
He has more depth.
That is why they come to him.

So on one example for me, I am a OK guitarist.
I am a musical producer.
But if you put me in a really big studio in charge of a whole band musical group, I had to record them, produce them in a big studio, I would be out of my depth.

Q: Maybe in Japanese,　we say CAPA,,,

Yeah, “within my capacity”, “beyond my capacity”.
That’s a very good other phrase to use.
That is “beyond my capacity”.
So the police is beyond their capacity.

beyond my capacity
私の手に余る、私の能力を超えている。

■出演
・ETCマンツーマン英会話トニー先生(荻窪/富士見ヶ丘)

■聞き手
・青樹洋文

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