The fish swam deeper and deeper, into the darkness of the ocean.

Meaning: The fish swam further and further down, where it was very dark.

Choice of Words: Darkness means the absence of light. It's like when you close your eyes and can't see anything.

Alternative Expressions

The fish descended further and further, into the abyss of the sea.

Meaning: This sentence describes a fish moving further and further down into the dark and mysterious depths of the sea.

Choice of Words: The fish is a noun that refers to a living creature that lives in water. Descended is a verb that means to move downward or to a lower level. Further and further is an adverbial phrase that means to go further down or into something. Into is a preposition that means to move or enter something. The abyss is a noun that refers to a deep and vast space or void. Of the sea is a noun phrase that refers to a large body of salt water that covers a large part of the Earth's surface.

The fish plunged deeper and deeper, into the murky depths of the ocean.

Meaning: This sentence describes a fish moving suddenly and forcefully further and further down into the dark and unclear depths of the ocean.

Choice of Words: The fish is a noun that refers to a living creature that lives in water. Plunged is a verb that means to move suddenly and forcefully downward. Deeper and deeper is an adverbial phrase that means to go further down or into something. Into is a preposition that means to move or enter something. The murky depths is a noun phrase that refers to the dark and unclear lower parts of the ocean.

Related Expressions