The style of the narrator in these verses is characterized by repetitions, which may be considered a literary device to picture the monotony of the constant rains and the gradual rising of the water.

The waters prevailed and increased greatly: prevailed translates a verb meaning to become strong, mighty, powerful. This word is repeated four times in verses 18-20, 24. It is also used, for example, in 1 Sam 2.9, where Good News Translation translates it “triumphs.” The poetic picture is of the growing might of the flood that is destroying all life on earth. For increased greatly see the previous paragraph. The two expressions may be translated “The flood waters swelled mightily and grew ever deeper,” or “The water rose higher and higher.”

Upon the earth is often considered redundant, as the earth is the only place where floods can occur. We may say, however, “The water rose higher and higher above the ground” or “The flood water became deeper and deeper on the land.”

And the ark floated: floated translates the common Hebrew verb meaning go, come, walk, move. It is used with reference to the sailing of ships, for example, in 1 Kgs 22.48; similarly 2 Chr 9.21. Good News Translation translates “drifted,” which suits the context well. Some other translations have “sailed around.” It will be good if the translation does not give readers the idea that the people in the ark guided or controlled it in some way.

On the face of the waters means “on the surface of the water” or “on the water.” Good News Translation has “on the surface,” meaning the surface of the water.

Quoted with permission from Reyburn, William D. and Fry, Euan McG. A Handbook on Genesis. (UBS Helps for Translators). New York: UBS, 1997. For this and other handbooks for translators see here .