The seasinger's robe top is Magic tank body armour made in the player-owned port minigame. It requires 85 Defence to wear, and 90 Runecrafting to make in the port's workshop, using 80 chi and giving 30,000 Runecrafting experience.
The seasinger's robe top lasts for 60,000 charges of combat before degrading to nothing - it cannot be repaired. Equipping the top will cause it to instantly degrade and become untradeable, even if it has not been used in combat.
When dying in the Wilderness a top will drop with its remaining charges intact.