I suck as Sea of Thieves Ship combat

Yeah. Don't play because a streamer told you it was cool now.

Don't be new. Play a lot and often. Practice.

Find a good crew on here.

Oh. And use a sword and a gun.

One thing at a time. Honing your aim with cannon is simply practice. Pick random things to hit on islands as you pass by, run the routine from the helm to loading. Skele-ships make for good moving targets. Join a larger ship with a combat oriented crew.
Cutlass, Cutlass, Cutlass.

There really is a lot that goes into ship combat. And a lot of players on the seas are missing skills with it, so don't feel too alone about that.

I'm not sure what ships you've been spending time on. Sloops, Brigs, and Galleons all have their differences. I highly recommend crewing on galleons with 3 others to learn the ropes. I also encourage solo slooping to get familiar with handling all aspects, but the sloop is a drastically different beast AND fighting others on a sloop is an extreme hard-mode, so I'd solo sloop just for sailing and stuff, but try and avoid PvP on the sloop for now (but everything you learn will help you in being successful at this as well).

With a crew - A crew that works together and works well can make all the difference in the world. So, crew chemistry and communication is important on the bigger ships.

SHIP REPAIRS. If the ship isn't getting repaired, the ship will go down. With Galleons, you need to know when there's a leak (you can hear a water rushing sound from top deck) and SOMEONE needs to race down there and repair right away.
BUCKETS are hugely important. If the water is rising too quickly, multiple buckets bailing the water can save the ship, while another crewmate repairs the hole. COMMUNICATION is huge here, as well as quickly recognizing when additional help is needed.

That's repairs though - let's talk more on the offensive combat side:
CANNON ACCURACY is a major skill that can spell the difference of a battle.
Some pirates have a feel for it and pick it up quickly, some do not.
Go out on the sea, find some good rocks, and fire your cannons on them. Aim for particular points and do this while the ship is moving, do it from varying distances, and do it from different ships. This can help you get the right feel for how the trajectory will play out and give you better accuracy with the cannons.

Against Galleons - AIM BELOW THE WATER-LINE!! Hitting a galleon in the upper deck will not put water into their boat (not until their lower deck is already full or they've been hit with a cursed ballast ball).
Spread your shots around the hull of your enemy's ship. Multiple locations mean multiple holes, quicker water, and more repairs needed.

HELM - The person on the wheel (whether it's you on a solo sloop, or one person out of 4 on a galleon) needs to keep their eyes open and their mind ahead of the game. With communication to the people working the SAILS, you want to keep maneuvering into favorable positions for your ship.

The truth is, the chaos and happenstance of the seas creates a lot of variables, also greatly depending on what ships are involved and what each crew's strengths may be.

You want to put your broad side on them, to fire your cannons, without letting them get the upper hand in shots against your ship.
Or you want to fire at the other ship's cannons, to keep them from firing on you, while also landing some shots on their lower hull.
There are lots of strategies, and the more you play ( and learn from others) the more you might learn to decide what to do in various circumstances.

SAILS, again, depend on the situation. However, you generally want to slow down and not be flying at full sails while you pass for cannon fire. Aiming and landing cannon shots while racing by at full speed is both extremely difficult, and mostly useless, because you'll only get 1-3 shots, at best, and even if you DO manage to hit them with it, you're flying by and they'll be able to repair after you've passed.

DEFEND YOUR OWN SHIP. Everyone needs to watch for boarders. There are sound indications of swimmers, of someone reaching your ladder and pulling themselves up out from the water onto your ladder. Listen and keep a visual check on your ladders.
You can also hear a different sound when a pirate shoots themselves out of a cannon. Become familiar with these sounds and always be at the ready to defend your own boat. Shoot them off of your ladder, or before they reach it, when you can.

If they manage to board your vessel, they may run towards your anchor to drop it and stop you from sailing.
If you fail to kill them before they drop your anchor, do not just begin to raise your anchor - they will be able to kill you easily while you're stuck trying to lift the anchor.

BOARDING THEIR SHIP
If the other crew is doing their job in repairing their own ship, you may need to board them and prevent them from repairing.
I see it like this - the ship is armor, and once you break through that, you hit the crew, to strike the final blows.

You need to time things well. You need to use communication with your crew (if you have one). Too many pirates all attempt to board the other ship, while their own vessel is left unrepaired.
If the crew can spare it, a boarder can use the cannon to fire themselves (or another crewmate with greater accuracy can do the aiming and firing) to either land on the enemy's ship, or ahead of it, in order to then grab onto the ladder and board.
You can also attempt to pull close enough to simply jump aboard the enemy ship OR you can get close enough to attempt a long distance leap and ladder grab.
Regardless, the tactics and skills that go into successfully taking out the other crew are a whole other story, heh.

Simple things to try to remember - cool minds prevail. Mindfulness, strategy, and patience can make the difference sometimes. If a person has a gun (or two), they can't hit you while you're behind an obstacle. A fired gun (or two, lol) cannot fire again until reloaded - so, waiting for, and avoiding/surviving, their shots, can then lead to you taking them out.

Now, these are just some things I could think of off the top of my head. And everyone is a different, of course.

One of the biggest keys, though, beyond COMMUNICATION and experience, is CANNON ACCURACY.

This game, though, having no in-game skill progression, truly does have an element of firsthand experience progression. Even watching other, skilled, players can help out (not necessarily the biggest, fancy streamers, but some of the smaller streamers that have been playing the game since day one, can really show you a lot, if you find yourself struggling). Even as a vet since before the game launched, I find myself learning a lot from watching others.

Oh, also, most importantly... HAVE FUN. And I also try to make sure I let my opponents know it's all in fun.

I've probably skipped over a lot, but I hope some of this may be helpful.

A quick simple note about the different ships
Sloop - slowest of the ships with full wind; fastest of the three ships directly AGAINST the wind; quickest turning (if you're trying to flee larger ships, or just gain some distance, aim directly into the wind and rotate your sails correctly)
Galleon - fastest of the three ships with full wind; slowest of the three ships directly AGAINST the wind; slowest turning
Brigantine - Medium between the two others in all speeds and turning. Faster acceleration than either.

I've found that hundreds, if not thousands, of hours of PvE has completely corrupted my PvP gun game. I'm completely terrible, to be honest, in PvP gun/sword battles. So don't try and get good with the skellies and then think you are going to be good in PvP.

@fusedflare80

For me naval combat comes down to four distinct roles, which have different priorities.

Now even though you have a crew and you set roles, you must understand it it fluid and situations call for the ability to adapt. More advanced or people that play often together don't even assign roles and can be extremely successful. My advice is learn them all, but the most important aspect in playing with a crew is communication.

The roles I personally believe are the following:

The Bilge Rat, they don't like the outdoors and sunlight I assume.

Their domain is the Hull.

Their priority is to keep the ship alive. They are the first to head down and patch up. They are the ones judging when they need help on bailing and can actually call every single man down there if needed. When they call, you respond and start moving.

Tip of the day: Bailing water is quicker than patching, so first ensure the water level is low enough for you to start patching.

TheHelmsman, enjoy the breeze in their hair and are shackled to the ship.

Their domain is the steering wheel and back sail.

Their responsibility is naval position, which is tricky and just requires practice and good shot calling of what you need from your other mates.

Tip of the day: Anchor is only used for 180 turns and dire situations.

The Deckhand, the master of none.

Their domain is the top deck: from ladders to cannons to all the remaining sails.

They are the ones pumping holes into other ships, first to come in action when others calls and guards those ladders.

Tip of the day: Watch your supplies and be proactive.

The Sea Dog, the boarder.

Their domain is anything outside the ship

They are the ones assaulting the ship, making the plays and providing the supplies.

Tip of the day: Learn when not to leave the ship and become a secondary deckhand.

• Naturally on a galleon you have all four
• A brigantine combines the Deckhand and the Sea dog.
• A sloop becomes more of a Captain (bound to the ship) and their trusty right hand man (Support and boarder).

Naturally your tasks might not always need attending, and jobs spill over into each other. Though usually it just means you help out the deckhand, be it ladder defense, sail management or blasting away at the enemy.

When playing priorities are quite straight forward:

1. Don't sink, keep that water out.
2. Don't get boarded, guard those ladders.
3. Don't get knocked off, in combat it can be worse than dying.
4. Don't die, it doesn't feel nice when being sent to the timeout zone and it means other people need to take over your role.
5. Don't get broadsided by your enemy.
6. Adapt to the situation at hand. Just because you had a role at the start doesn't mean you shouldn't be doing the other ones when needed. It is a team effort after all.
7. Make use of cursed cannon balls (still have to do this myself more often, one of my major flaws).
8. Dealing with enemy (potential enemy) pirates has priority over everything PvE related, including loot.

Above all: keep communicating.

I know that 'sneaky' is cool and all that, but in combat it is more important that people know what you are doing. So even 'hot' micing it can be useful if not using a party chat or discord or something else. Your crew needs to know the situation, as a boarder you need to know whether you should be rushing back, as a helmsman/deckhand you need to know an enemy is coming or you are sinking, etc. and even knowing where the other team is by reports from the boarder can be useful. They have multiple people below deck, they are not at the cannons and all that can help the helmsman position the ship with taking less risks. I usually don't talk too much to the enemies, I am talking to my crew and could care less what the enemies think of me or know that I am coming for them (I love being the Sea Dog that calls the shots in my crew, the helmsman only calls the shots for naval positioning, combat wise it could be anyone even a bilgerat with enough information being given (hardest person to do it though)).

Once you know your crew and know that you can rely on them doing their job and they can rely on you doing yours the issue of feeling the need to do everything is reduced and avoids everyone doing the same thing (like all jump off on to the other ship and there goes your ship or a single hole being your demise). That's why assigning roles at the start is a good thing for less experienced crews or people that enjoy variety (don't do this at the start of combat).

Warning: When things go south, don't try to point fingers too much of you were suppose to X as the Y and such. Rant for 5 secs, get over it and focus at the task at hand: recover, bounce back, what needs to be done NOW to turn it around. The past is the past, what was done is done.

In the end, analyze your wins and losses. Where did it go wrong, why did it go wrong and was it due to a mistake on our end or was it by not understanding the mechanics or did we just get outplayed and in these cases what did they do differently? Adapt accordingly and become a better pirate. Practice makes perfect.

Tip: Skeleton ships are a pretty decent entry level to practice the basics, as you don't have to worry about boarders or gunpowder barrels.

Now, I could write a book on steering, navigation, use of your environment and go over tons of scenarios, but in the end it is practice and learning from your mistakes. Using what is in your control and how you enjoy playing to provide you with the best approach. Try out tactics, experiment and don't be too harsh on yourself and enjoy the battle, remember sinking provides the best lessons.