This is my first solution for this site so any constructive criticism you may have will be appreciated. Be gentle. Now, on with the show.
Sea Legs 30G Complete all Naval Contracts.
These will start to appear after you capture the forts dotting the map. Some are easier than others. I'd recommend upgrading the Jackdaw some before attempting these. High end mortar shot will make these pretty simple, but there are two or three contracts that can get hectic if you're not prepared. Each captured fort also has a Harbormaster so stock up on ammo or repair the Jackdaw as needed. You can gain a large amount of materials for upgrades or ships for Kenway's Fleet by doing these.
I did these in one sitting. With some pauses to make notes it took about three hours. The difficulty rating is the game's, not mine. We will start in the NW area of the map and move clockwise.
Dry Tortuga (254,749)
~ Private Escort
reward: 2400R - difficulty: 5
Locate and protect a vessel from a small Spanish fleet (gunboats and brigs). If you stray too far away you will be desynced and fail the mission. Sink them or board them to pass.
Eleuthera (726,784)
~ A Spanish Plague
reward: 1200R - difficulty: 1
Sink 3 Spanish gunboats.
I found a mess of British ships right where the contract starts, but no Spaniards. Sail towards Cuba's northern shore and they will start to appear. Schooners and Brigs won't count.
Gibara (657,521)
~ Silk on the Waves
reward: 1200R - difficulty: 2
This guy wants 30 measures of cloth. I had enough in my inventory already so this was short. If you don't have enough, just go hunt and take ships until you do. You might as well save up some wood for later while you're at it.
Punta Guarico (776,399)
~ Weathering the Storm
reward: 1200R - difficulty: 1
Find and destroy and small British flotilla in some foggy and windy seas. Just some Brigs and Gunboats, nothing crazy. Mortar shot makes short work of this one.
Navassa (728,219) two missions
~ Blind Justice
reward: 1800R - difficulty: 4
Locate and capture a British Man o' War.
This one has three Brigs protecting her. Deal with them as you see fit, then board the Man o' War, and kill the captain. Don't sink it (I sent it to Kenway's Fleet afterward).
~ A Personal Matter
reward: 1800R - difficulty: 4
Find the HMS Defiance.
I found this frigate hanging out with two other frigates, two brigs and some gunboats. You can fight them all if you want, or single out the Defiance like I did. The contract ends once the Defiance is taken care of.
Cabo de Cruz (566,390)
~ Driftwood
reward: 1800R - difficulty: 4 (seriously?)
Remember before when I mentioned you should gather some lumber while plundering? This guy wants 60.
Castillo de Jagua (356,559)
~ Eye for an Eye
reward: 1800R - difficulty: 3
Board and capture the Spanish frigate San Lorenzo. The ship was alone when I found it. Straightforward as can be. Board her, and then do want you want afterwards.
Charlotte (470,272) two missions
~ Hunter Gatherer
reward: 2400R - difficulty: 5
Stock up on ammo before this one. The guy wants you to sink two British pirate hunters. I had two frigate and three brigs spawn close to the starting point for this one. Attack them, board them, sink them or do whatever. Just raise your wanted level. The hunters will find you after you cause enough mayhem.
~ Papers, Please
reward: 2400R - difficulty: 5
Find the HMS Courage, British Man o' War. I found this ship without ant type of escort. Sink the ship.
Chinchorro (124,357) two missions
~ Contraband
reward: 2400R - difficulty: 5
Sink one Spanish frigate and two brigs. I found them all just NE of where this mission starts. Board them or sink them; it counts either way.
~ Smuggler's Den
reward: 2400R - difficulty: 5
This is the trickiest one so far. Stock up on mortar shot before you start this one. Sail to the waypoint and you'll find a Man o' War, two frigates, and at least two gunboats blockading a narrow channel. Move in so they are in range of your mortars and line up a shot centered on the Man o' War, but with the smaller vessels taking some damage. They will come after you as soon as that first shot lands. Let them chase you into open waters while raining more mortars on them. Focus on the Man o' War as much as possible and pick off the smaller vessel as you can. It can be tricky, but don't lose your cool.
Conttoyor (102,547) two missions
~ The Law of the Ocean
reward: 1800R - difficulty: 3
A piece of cake after the last one. Sail to the ambush location. After a small cut scene, a brig and two gunships will appear. Destroy the gunship, then board the brig and kill the captain.
~ The Realities of War
reward: 2400R - difficulty: 5
Locate your allies (I found them just to the NNW) and follow them into two waves of Spanish ships. The first was two brigs, followed by two more brigs and a Man o' War. Your allies WILL get in your way. Destroy, sink or board the Spanish ships as you see fit.
Serranilla (347,140)
This will only become available after all other contracts are completed.
~ The Final Contact
reward: 2400R, Golden Flintlocks, 30G achievement - difficulty: 5
Make sure you prepare for this one. upgraded hull strength, mortar damage and capacity and heavy shot damage will make this much easier.
Locate the Hollander.
Just to the north you'll find a Man o' War flying the Jolly Roger in serious distress. Protect this ship at all cost. Several waves of British and Spanish vessels will attack in (for me at least) stormy conditions. The first wave of four gunboat is simple enough. The second is two brigs and a frigate, followed by two frigates and a Man o' War. Use your mortars frequently, and put yourself between the attackers and the Hollander. If you start to get in trouble, board a ship and use it to repair the Jackdaw. It can be tough if you're not prepared, but a straightforward fight otherwise.
Congrats.
Comment with questions or suggestions. Depending on the response I may start writing more solutions. I'm not entirely sure if the weather events are scripted with these contracts or not.