There is a ship that crashed and drowned on the southern shore of Solstheim. The shipwreck is located south of Raven Rock. A good time to explore it would be while doing the quest "March of the Dead", since the ship wreck is located very close to the Old Attius Farm. See map below for exact location of the Shipwreck:
Approach the ship, and prepare to fight. The main enemies here are Reavers, which are like a Dunmer version of the regular bandits. Variants of this enemy include the Reaver Marauders, Reaver Outlaws, Reaver Plunderers, and Reaver Lords. Don't expect a warm welcome, draw your weapon and kill these enemies.
There is a Heart Stone Deposit just outside the entrance to the ship. Heart Stones are used when summoning Ash Guardians, they make it so that the Ash Guardian is not hostile. Without a Heart Stone in your inventory, the Ash Guardian you conjure would be hostile. Neloth will also be willing to buy the Heart Stone from you.
Board the ship. There is a bunch of loot on board, including coin purses on a small wooden table, some books, weapons, food, Adept Locked chest, and other random stuff.
Go to the lower deck, and keep searching for loot. On the shelves, make sure to loot the East Empire Company Strongbox, located on the bottom shelf. In an adjacent section, there is a caged skeleton with some coin on it. Some more skeletons lay on the floor, carrying more gold and potentially some Bone Meal. Also look for a big chest near the wall, containing a book called "Lusty Argonian Maid Folio" which is needed for the Misc quest: "Return the Folio to Cindiri Arano in Raven Rock"
For more info about the Shipwreck, see the video games wiki:
Skyrim Dragonborn: Wreck of the Strident Squall
