This is an idea that is dear to my heart and I'm looking forward to running a pirate/naval adventure myself. I've got some inspiration ideas for you!

Books

These books should need no introduction. These are the books that will truly inspire your game.

• Necronomicon: The Best Weird Tales of H. P. Lovecraft
  
• Eldritch Tales
  
• Conan the Barbarian - The Original, Unabridged Adventures of the World's Greatest Fantasy Hero
  
• Grimms Complete Fairy Tales
  
• Tales of Norse Mythology
  
• Iliad and Odyssey
  
  

  TV Shows
  

• Crossbones - This is one of the most underrated TV shows I've ever seen. It got canceled late in it's first season and so the finale was rushed, but despite that it's an amazing show. This show has political intrigue and adventure ideas abound. I'd argue it's damn near required viewing for running any sort of pirate campaign.
  
• Black Sails - This amazing show is written as a prequel to the novel, "Treasure Island". It follows Captain Flint, and a young John Silver as they attempt to make an "honest" living while preparing to thwart the predicted demise of piracy. Swashbuckling adventures, intrigue and more adventure ideas here than I can count. The show is a hell of a ride and I can guarantee you'll get plenty of ideas watching this one.
  
• Vikings - This show is the show that just keeps on giving. The first two or three episodes are a little slow to start, but you'll be on the edge of your seat every episode thereafter. While this show focuses on vikings, there's plenty here to inspire a pirate adventure. It will especially inspire the creation of your villains.
  
• The Musketeers - This isn't that terrible (and oh so amazing) Disney movie from the 90's. This show focuses on the Musketeers you know of, and the Musketeers as a military unit during that time period. If you're focusing on adventures during something similar to the golden age of piracy, you need to watch this show. One of my favorites.
  
  

  Tabletop Books
  

  
  

• The 7th Sea - I am not recommending this as the system you should use, I am recommending it strictly as inspiration for your setting. It easily has the most interesting setting I've ever seen and has some amazing ideas for adventures dealing with curses, the sidhe, naval campaigns, city adventures, etc. Whether this will be useful to you depends entirely on your setting. Are you playing D&D on the high seas? If so, this isn't going to be nearly as useful. Are you playing in a setting reminiscent of the golden age of piracy with some light magical touches (eldritch horrors in the deep sea, curses, magical fey creatures and low magic for the players)? If so, good lord is this book (and the Nations of Theah books) going to be useful to you.
  
• Razor Coast - If you're playing D&D on the high seas, this is the book for you. It's a sandbox setting with a ton of adventures and adventure seeds. It is expensive, but it's worth every penny. Highly recommended.
  
  I can't recommend all of this enough. A lot of this will give you ideas and inspiration for all of your campaigns, naval/pirate or otherwise. Have fun!