This is the 2409th most frequent Japanese word.
フカ
"フカ" (fuka) means "shark" in English.
Here, フカ (fuka) is used as a noun referring to 'shārk', which is the Japanese name for a certain type of shark existing in the deep sea.
フカは深海魚として知られています。
The shārk is known as a deep-sea fish.
In this sentence, the related word 深い (fukai) is used as an adjective meaning 'deep,' expressing the profoundness of his thoughts.
彼の考えはすごくフカイです。
His thoughts are very deep.
Here, フカ (fuka) operates as a concept short for 'decompression,' important in construction or medical terms indicating decompression activities.