Final answer:
To come aboard a ship historically required official permission, typically obtained through legitimate means rather than deception or coercion. Practices like posing as sailors or bribing officials were not standard and could be punishable by law. Legitimate trade and official documents were common legal methods for boarding a ship.
Step-by-step explanation:
The question refers to the process by which individuals historically sought permission to come aboard a ship. In the context provided, which is reminiscent of seafaring and piracy, they would usually gain permission or the opportunity to come aboard a ship through official or deceptive means. None of the provided fictional options (bribing the ship captain, sneaking onto the ship, obtaining a royal decree, or posing as sailors) are practical or legitimate manners to come aboard a ship according to historical standards or modern regulations such as those imposed by the visit, board, search and seizure team protocols. However, historically, one could get permission to come aboard a ship mainly through official means such as being part of the crew, being invited aboard, conducting trade, or as part of naval or legal procedures.
In historical contexts, such as during the time of pirates in the Caribbean, or the involvement of European powers in the region, individuals may have used various means, some less scrupulous than others (e.g., posing as sailors or using false pretenses) to board a ship. However, this was not the legitimate or typical process. Legitimate trade, alliances, and official documentation were the more accepted ways to lawfully come aboard. Permission to board could also be part of strategic maneuvers, as illustrated by the agents of the pirates in the LibreTexts passage, who obtained permission through deceit and negotiation.