The main reference for today is Rv 18:17-19.
The sea, ships, sea captains, sailors, and passengers in Rv 18:17-19 are all used figuratively. The sea represents the world (Dn 7:2, 17), the ships represent the churches of the world (Gn 6-8; Is 51:5; Rv 8:9), and the sea captains represent the pastors of the world. The sailors are evangelists, the passengers are congregation members, and those who earn their living from the sea are church officials. All of these people have sold the goods of the spiritual nation of Babylon. In other words, they have used the doctrines of Babylon to evangelize others. These goods, which represent the doctrines and teachings of Babylon, will no longer be purchased after God judges Babylon and reveals her goods to be false.
Before this judgment occurs, the people of Babylon failed to realize that their churches and denominations belonged to Babylon, the kingdoms of demons (Rv 18:2-3). They also had no idea that their doctrines were the teachings of the devil. They believed that their teachings were true and orthodox, which is the reason they did “business” with those teachings. Once their doctrines are revealed to be Satan’s teachings, however, no one is willing to buy (believe) their doctrines. This is why the people of Babylon weep and mourn. Since these people of Babylon entered the tabernacle of heaven and destroyed its chosen people in Rv 13, wouldn’t a person from the tabernacle of Rv 13 know who they are? Surely he would have seen them. Surely those who were victorious over the beast, his image, and the number of his name from Rv 13—the victors who escaped the tabernacle according to Rv 15—can testify about the events that took place in that tabernacle because they witnessed them. Surely they know very well who the destroyers really are.
In summary, the people of the spiritual nation of Babylon (the kingdom of demons) used the Babylonian doctrines and teachings to grow rich. They achieved this via the might of Babylon’s excessive luxuries (its ecclesiastical authority). Babylon’s churches are called ships and its leaders (kings or pastors) are called captains. Babylon’s sailors represent her evangelists. Those who understand this at the time of judgment will cross over from death to life—from Babylon to the place where the Lord truly dwells (Rv 17:14; Rv 18:4; Mt 24:15-16). In doing so, they will attain salvation.
This is the testimony of the one who saw what took place at the location where the physical fulfillment occurred. This is why this testimony is true (Rv 1:2; Rv 22:16).