Revelation 18:19

they threw dust on their heads
An action indicating great mourning and grief over loss (Jos. Jos. 7:6; 1S. 1S. 4:12; Lam. Lam. 2:10; Eze. Eze. 27:30). Here, the loss is their commercial market.

that great city
See commentary on Revelation 18:10.

in which all who had ships on the sea became rich by her wealth
Like the kings who had lived luxuriously with her (Rev. Rev. 18:9+) and the merchants who had become wealthy by her (Rev. Rev. 18:15+), those who made a living by shipping had become wealthy. She is a great center of commerce and a major destination for shipping. See commentary on Revelation 18:17.

in one hour
The mariners repeat the same lamentation as the kings (Rev. Rev. 18:10+) and the merchants (Rev. Rev. 18:17+) concerning the suddenness of her destruction. See commentary on Revelation 18:10. This threefold pattern of lamentation is intended to indicate the completeness of her destruction. See Three: Life, Resurrection, Completeness, the Trinity.

she is made desolate
See commentary on Revelation 18:17. See Babylon’s Predicted Destruction.