Guinevere Tinsley has sent along word through the usual channels that she's found a "profitable voyage" for your upstrart troubleshooting business.
1) Nation NPC "has sent along word through the usual channels that she's found a 'profitable voyage' for your upstart troubleshooting business. Meet with her to learn the details."
2) "A merchant named (NPC 2) is interested in hiring you for a 'profitable voyage' of some sort." Nation NPC "has arranged a meeting with (NPC 2), proceed to the location marked on your charts and find out what, exactly, this voyage will entail."
3) "(NPC 2) has engaged your services as negotiator for his next convoy. He has every expectation that the convoy will run into pirates along the way, and wants to ensure that his ships survive any such encounter, even if he loses some cargo. If you do encounter pirates, raise the white flag of surrender, and then prepare to talk your way out of the situation."
There's no sailing involved here, you simply start the mission and end up on a ship. Talk to the crew and then talk to the pirate captain. You will have to duel the pirate captain (he surrenders if you beat him enough).
4) "Though (NPC 2)'s convoy did indeed have a run-in with pirates, you were able to negotiate an amicable transfer of goods to the buccaneers without losing any of (NPC 2)'s ships in the bargain. It was not a pleasant negotiation, but it was the only way to ensure at least some of the goods and all of the merchant vessels survived."
5) "You have completed a strange and difficult negotiation with some remarkably talkative pirates, and (NPC 2) is satisfied with the amount of goods you were able to save -- and delighted that none of his ships were lost. His assistant will handle the small matter of your pay."