Adventurers formerly had to complete a questline beginning with The Cove of Decay - Prison Break in order to gain access to this instance. This is no longer required, however adventurers can still obtain and complete the quest series.
This instance is the first version of the zone, there are several different versions of this zone, ranging from Solo to Raid:
Cove of Decay was originally under the watchful eye of The Great Herd, however undead overtook the area and the centaur were forced to seal off the cove using a magical spear known as Stormsunder. Through a series of perilous trials, an adventurer was able to gain the centaurs' trust, reform the spear, and gain access to this accursed zone. Now there's nothing but hordes of undead and sea-beasts between you and the shipwrecked treasure held within.
The entrance to the the instance and the beach itself are infested with undead. Return them to their graves. Then enter the water and slay any bothersome sea-life.
Hovering above a shipwreck at the inlet of the cove is The Octagorgon, a mythical octopus whose ink is of particular rarity.
Once The Octagorgon has been dealt with swim down to the shipwreck at ( -262, -50, 1321 ) /waypoint -262, -50, 1321 and retrieve Partially Digested Hand from the chest. Return to the beach, go to the firepit at ( -152, -22, 1174 ) /waypoint -152, -22, 1174, interact with the pile of bones and choose the option "place the skeletal hand in the flames". Captain Ulssissaris, presumed captain of the ship that The Octagorgon destroyed, will spawn. Kill him to complete the instance.