Jeremiah 51:42 New English Translation

⁴²The sea has swept over Babylon.
She has been covered by a multitude^[a] of its waves.^[b]

Jeremiah 51:42 tn For the meaning “multitude” here rather than “tumult,” see BDB 242 s.v. הָמוֹן 3.c, which says that this refers to a great throng of people under the figure of an overwhelming mass of waves. The word is used of a multitude of soldiers, or a vast army, in 1 Sam 14:16 and 1 Kgs 20:13, 18 (cf. BDB 242 s.v. הָמוֹן 3.a for further references).
Jeremiah 51:42 tn Heb “The sea has risen up over Babylon. She has been covered by the multitude of its waves.”sn This is a poetic and figurative reference to the enemies of Babylon, the foe from the north (see 50:3, 9; 51:27-28), which has attacked Babylon in wave after wave. This same figure is used in Isa 17:12. In Isa 8:7-8 the king of Assyria (and his troops) are compared to the Euphrates, which rises up and floods over the whole land of Israel and Judah. This same figure, but with application to Babylon, is assumed in Jer 47:2-3. In Jer 46:7-8 this figure is employed in a taunt of Egypt, which had boasted that it would cover the earth like the flooding of the Nile.

New English Translation (NET)