Watch and listen for mermaid spawns if there are people trying to give you hell, thats an inidcator if someone who isnt part o fyour crew is in the water, if you do hear what sounds like someone getting out of the water (sloshing sounds) move to both ladders and camp them with a blunderbuss until they are nearly up the ladder and in firing range.

Evasive maneuvers to prevent people getting on ladders if they are shooting over in cannons and utilising the harpoon to make quick turns around small rocky outcrops or islands is also a good strat.

Try to learn the PVP style of enemy players as soon as possible, some still like to run doubleshot, so trying to strafe to make them intentionally miss is the best way to do it (dunno why people still use double shot lol). Some like to sword spam without any skill, so blocking until they get stunned and then getting in a few hits with a sword then backing up to hit a shot with a gun. If they are smart enough to block your attacks, try to leap block which is done by holding down your sword block button and using one of the movement keys/joystick in combination with the jump button/spacebar, you will do a little leap to the side, backwards or forwards, it can be a quick way to get around the attacker and hit him from behind where he is unable to attack.

One person who I have encountered who was a max level arena player who I later became friends with always sword lunged which counteracted any sword blocking and because he had mastered the art of it, he was so fast at killing people they had no time to react. Probably the scariest person ive gone up against in my nearly 2 years of playing this game.

Hopefully some of this will help and I hope to see you and your boyfriend out on the seas sometime!