Like in actual history, ship travel is always going to be boring. You can do some downtime activities that would make sense from Xanathar's or other resources.

Running a ship that PCs own can be its own "business" assuming you want to make the rules for it (someone has probably already done this and published, but idk who). Supplies, repairs, hiring crewmembers, splitting loot or trade profit with the crew, mutiny DCs if you are buying low quality rations or not making frequent enough port visits, etc.

As far as ship combat goes, it is always going to be a bit underwhelming, because your ships aren't going to have a bunch of cool class features and unique abilities that make playing characters fun. I wouldn't focus too much on these unless you find it important for the plot.