This is the 2703rd most frequent Korean word.
심해
"심해" means "deep sea" in English.
In this sentence, '심해' is used as a noun referring to the deep sea.
심해는 깊고 어두운 바다의 일부입니다.
The deep sea is a part of the ocean that is deep and dark.
Here, '심해' is part of the verb '심해지다', which means 'to become severe'.
현재 대기의 오염이 점점 심해지고 있습니다.
Currently, the pollution of the atmosphere is increasing in severity.
In this sentence, '심해지다' is again used as a verb, meaning 'to worsen'.