Next add some nautical wall decor such as a photo of a ship on the sea, a lighthouse, etc.
Then set one or more nautical figurines on your sink vanity or any tables you might have in your bathroom. Even the back of a toilet will suffice. Consider large seashells, antiqued fish, a sea captain, a lighthouse, and so on. Or a large hurricane lamp with nautical rope inside is simple, yet looks exquisite.
Voila...you now have a bathroom with a nautical flare, and it's charming and sophisticated! Easy as pie, right?