The graveyard of ships is a place where are many shipwrecks in the Tartarus Trench.
Prior to Seabound
At one point, ships began to dive into the Tartarus Trench, and their graveyard was created at one point. As Kalmaar began sinking the ships, the graveyard grew even larger.
The Tale of Benthomaar (flashback)
When Kalmaar swam with his brother over the Tartarus Trench, Benthomaar notices several shipwrecks and asks him if it's safe. Later, he is startled by a skull sticking out of one of the wrecks.
When Trimaar learns that Kalmaar has sunk the Hydro Bounty in this place, he asks him if he's still sinking ships, to which Kalmaar tells him with a lie that he doesn't.
- In addition to "Unsinkable" and "The Tale of Benthomaar", it also appears in the opening sequence for Seabound, where a ship similar to the Titanic appears.