As the Wormwood sails into merchant shipping lanes, the team are given lessons in boarding a vessel with grappling hooks and climbing.
Level-2 climb checks being what they are, they also got some practice at swimming.
That night, it begins to look at lot like fish-men, as a raiding party of sahuagin deep ones attack the ship. The PCs are instrumental in seeing them off.
The next day, merchant sails are sighted on the horizon, and the Wormwood closes in on its prey…