How did ancient pirates find passing merchant ships in the vast sea?

Ancient pirates were able to find the past merchant ships in the vast sea because: the ancient routes were generally fixed; And the time period is relatively fixed; There is also the date when merchant ships or specialized agencies sometimes sell merchant ships and sail. Merchant ships can only temporarily avoid the interception of pirates when changing their routes. In addition, the sea surface is sometimes unstable, so the route is generally cautious.

When we watch the movie Pirates of the Caribbean, we will be infected by the plot and impressed by the bravery and agility of the pirates. So how did pirates practice, or how did they successfully find merchant ships in the vast sea? I think it includes the following points:

Ancient routes were generally fixed.

This is because the sea is not facing the land. We can see the things on the land clearly at a glance, but the sea has a deep mystery. There are undercurrents in some places and reefs in some places; In some places, sharks have an impact on the route, and because the land is divided, it is usually air mail.

The time period is also relatively fixed.

The route is fixed, and the time period is relatively fixed, which is reflected in the peak season and there are more sea transportation. This time is also the time when pirate ships haunt. As pirates, more people will be sent to intercept them and get the treasure on board. This fixed place and time provide convenience for pirates to find merchant ships.

The date when a merchant ship or specialized agency sells a merchant ship and sails.

In addition, pirates, like bandits, are mercenary, and they also buy and sell information about merchant ships through similar spy agencies in the middle, which gives them a bigger bargaining chip in finding merchant ships. In addition, pirates will train sentries and other personnel to inquire around and collect such information.