You're 100% sure that whoever finds your storage box full of chains, cannonballs, pineapples and some cursed balls will use them to sink innocent people and ruin their so called "gaming experience".

They paid for their game and they deserve to live their well deserved PvE content but there are many evil pirates roaming this planet, the money they paid for the game is not important because they enjoy griefing and shooting and making weird noises on their mics as their fire their cannons at people to hurt their internet feelings.

...you don't want that, do you?.

So im not really sure what happens to buried treasure once you log off, been googling for a while and nobody seem to have a definitive answer of how it works.

But anyway just in case the buried stuff won't magically dissapear once we do:

The idea is to get everything into storage crates and bury them at some weird place at an outpost or island then you get the map and drop it between rocks or debris or just at the hideout in the tavern, wherever is hard to see it's glow so only true pirates might find it, of course assuming this things won't inplode after you changed session or logged off.

Just scuttle as close from the sovereigns as possible, if you're lucky enough the barrels will spawn near, just harpoon the barrels and drop them again and they dissapear mysteriously.
Then hide all empty storage crates on top of the tower, if the next crew to spawn at that outpost is smart enough to look up they deserve to have them.

Put everything in the rowboat storage and sink it with blunder bombs. Rowboats can't be looted once once sink and they don't drop barrels either.
If you don't have blunderbombs you can sink it with the harpoon, it takes a bit tho.

Sometimes the rowboat storage is not big enough to put everything so i hope you have some storage in your stomach to eat a bounch of food, you can leave the bananas in the barrels as nobody cares about them anyway and make sure to use your fireworks and flares to make even more space.

If you happen to have saved a check point for the third episode of this tall tale 3, you can open the portal and throw your ship in. Once you're on the other side you're free to log off.