Which one of the following self-made sentences sounds more natural:
- They are under the surveillance of the intelligence agency.
- They are under the Intelligence Agency’s watchful eyes.
Do these two expressions have different meanings or they can be used interchangeably? Based on dictionary definition about surveillance I guess it would be better to use the former sentence, although both mean the same and both are formal.
They mean essentially the same thing, but "surveillance" is far more formal.
If you were a law enforcement officer or intelligence agent writing a report on your activities, you would definitely say, "We placed the suspect under surveillance", and NOT "We kept that guy under our watchful eyes".
Also, "surveillance" is normally understood to mean watching someone for purposes of gathering information about a crime or act of espionage, while "watchful eye" is far more general. You could say, "Sally kept her children under her watchful eyes while they were at the park." You would be very unlikely to say that she "kept her children under surveillance" ... except as a joke meaning excessive watchfulness.
It depends on the context.
They are under the surveillance of the intelligence agency.
Sounds serious and official, implying the surveillance is reasonable and/or justified.
They are under the Intelligence Agency’s watchful eyes.
Is somewhat casual and dismissive. "Oh, you snuck a bottle of water into the airport, however did you get past TSA's watchful eyes!?"
It could also imply that the agency is just watching and not doing anything about them.
They can be used interchangeably. The only problems are that watchful eyes is fairly informal and is quite poetic. As a result, I would refrain from using the latter sentence in a formal and/or official setting.
