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!

The state of Conan ebooks is REALLY iffy. Anyone can rip the text from Project Gutenberg, run it through Calibri and add it to Amazon. (Well, not exactly--but you get the idea.)

Compounding the problem is that these things get pulled all the time, usually for formatting issues. I have two different versions of the same Conan collection in my Kindle library, neither of which is for sale anymore.

My advice is: Either stick with free resources like Project Gutenberg, or shell out for the superb three-volume Del Rey Conan collection. These are the primo, A#1, fully guaranteed versions. The price is steep, but it brings a certain peace of mind that you're getting the real thing edited by actual humans, and not some machine generated nightmare riddled with mistakes. If you like turning pages, used physical copies are considerably less.

They also come packed with cool artwork.

But yeah, either go big, or go free (so you have nothing to lose). Anything in between is probably a cash grab.

A book I can't recommend enough if you're interested in building a familiarity with Indian/Chinese/Japanese type gaming is Oriental Adventures from 3rd edition era Dungeons & Dragons.

https://www.amazon.com/Oriental-Adventures-Dungeons-Dragons-Supplement/dp/0786920157

or the PDF version--

http://www.dmsguild.com/product/23426/Oriental-Adventures-3e?term=Oriental&test_epoch=0&it=1

They made a free setting called Mahasarpa as an Indian, Southeast Asian flavored realm, as well as Rokugan (in the book) the d20 version of the Alderac game setting is a great samurai era Sengoku Jidai-ish Japanese setting, if you're looking for models.

Sounds like a good idea, like everyone has said already.

If you can, get yourself a copy of the Draconomicon for getting more details on how the dragons are and live and what not, I can't vouch for other versions, but the 3.5 Draconomicon is written in a very neat way like an explorer/naturalist writing their observations in a journal.

Many of the 5e modules have sections about running them in other D&D settings, so they are easily adaptable.

The Sword Coast Adventurer's Guide is the campaign setting book for the FR, thus far. Tho I also recommend Dungeonology by Matt Forbeck. It's a pithy little FR campaign primer and has THE best Sword Coast map produced in 5e, to date.

https://www.amazon.com/gp/aw/d/0786965800/ref=pd_aw_fbt_14_img_3/167-2967996-5756223?ie=UTF8&psc=1&refRID=2HSMNV0WGXZWD01G04RC

https://www.amazon.com/Dungeonology-Ologies-Matt-Forbeck/dp/0763693537


My favorite out-of-a-can campaign setting is actually Mystara. After I finish my next couple FR games, I'm gonna run a 5e Mystara campaign.

You can use any campaign setting book from any edition in 5e. You're just using the flavor text to tease out the world. Don't worry about the edition mechanics.

When I started making my homebrew setting back in the late 90's I used Richard Baker's World Builders Guidebook to help me design everything about the world. This book is phenomenal and will help you lay out things that you might not be thinking about, like size of the globe and weather patterns. Yes, the best advice is that you can follow is to remember that you do not need to complete the entire world when you start to design it, but from my perspective it helps to have a skeleton framework to build on when you do start out on that world.

Check out https://forgottenrealms.fandom.com if you're going to be running in the default setting. If one your players want an urban campaign, WotC just finished releasing 2 campaign books that take place in the city of Waterdeep. Dragon Heist can take them from levels 1-5, and it ends >!with players making 500,000 gp!<. If they don't feel like leaving the city you can run Dungeon of the Mad Mage until level 20 while taking breaks from the mega-dungeon to run their tavern or do any other adventures you feel like making up.

If you're not that into reading wikis I sometimes watch this guy Jorphdan's videos who just explains forgotten realms lore.

Lastly, if neither of those adventures sound cool to you check out adventure lookup's selection of adventures that take place in cities. Unfortunately I can't link you directly to the results, but just check "City/Urban" under the "Environments" tab on the left.

Hope that helps!

If you're interested in the Netheril Empire, there is a AD&D Supplement called "Netheril: Empire of Magic". (link just to show the product, I'm not suggesting paying 150 bucks for this)

I'm not sure where one would be able to get it legally for a more appropriate price, but I'm sure that you could be able to get your hands on a pdf.

Folk tales - preferably from non-Western traditions like :

https://www.amazon.com/Great-Fairy-Tale-Tradition-Straparola/dp/039397636X/ref=pd_sim_14_1?_encoding=UTF8&psc=1&refRID=RR4X6Y2X4TETCFG0YXEH

or

https://www.amazon.com/Folk-Fairy-Tales-Martin-Hallett/dp/155111898X/ref=sr_1_14?ie=UTF8&qid=1504822416&sr=8-14&keywords=folk+tales

I've been doing some world-building myself, and these are the links that I've found that help me the most:

- medieval demographics, based on data found in this book

- magical medieval society, a 3e reference book

- travel speed discussion

Both books are on Amazon as Kindle and Paperbacks.

https://www.amazon.co.uk/Priest-Ratcatchers-Book-Fantasy-Hardboiled/dp/0615512151/ref=sr_1_1?s=instant-video&ie=UTF8&qid=1500495641&sr=8-1&keywords=Matt+Colville

https://www.amazon.co.uk/d/cka/Thief-Ratcatchers-Two-Fantasy-Hardboiled-Matthew-Colville/0692203214/ref=sr_1_2?s=instant-video&ie=UTF8&qid=1500495641&sr=8-2&keywords=Matt+Colville

Art and Arcana

I think it's this !

In Numenera pilgrims are known as Peregrines.

Which led me to use the term Reynards for adventurers.

In one WM game, the players became known as "Harvesters". They skinned the hell out of everything they came across to get trophies to sell in the gold for Exp game. Since the bordertown they West Marches game operated out of was known as Hounds, I suppose that makes them The Harvesters of Hounds.