nature of displacement divided by a vessel's beam (breadth) (albeit with a constant multiplied to provide an average assessment), means thorough assessment of ship stability, immersibility and buoyancy involves other factors to address the relevant risks posed by waves, tides, weather and occurrences such as damage and collision. Large vessels In a storm, even large vessels may be rolled by being hit broadside by a large wave or swell or "pitch poled" stem over stern in extreme waves. This is normally catastrophic for larger ships, and smaller yachts can be dismasted (i.e., lose their masts and rigging) due to the drag as the boat is forced to roll over. A ship that sustains a hole or crack ('is holed') may capsize. This is the working of torpedo and naval mine warfare. In 2012 the very large cruise ship was holed and lost her propulsion by a mapped rock near the shallows, and drifted further where she partially sank, resting towards one side with most of her structure out of the water. This was not a capsize as her bottom was only partly exposed; rather this was a partial sinking. Fixing a hole is called plugging. Otherwise a vessel in largely upright position which capsizes has suffered too much water to enter in places normally above the waterline, and which may be caused by poor manoeuvering, overloading (see Plimsoll Line) or poor weather. As for holes, bailing may be carried out – removal of water aboard such as with a bilge pump, self or hand bailer or buckets. At the stage of sinking where its buoyancy is deemed critical, the ship is unlikely to upright nor able to right itself such that stability and safety will be compromised even if the vessel is righted — a decision is made to abandon ship and any ultimate salvage may entail firm grounding and re-buoyancy pumps. Among ship types, a roll-on-roll-off (RORO or ro-ro) ship is more prone to capsizing as it has large open car decks near the waterline. If the watertight car-deck doors fail through damage or mismanagement (as in the partial sinking of where the doors were accidentally left open, and as in one of the largest peacetime maritime disasters when MS Estonia sank off of the Archipelago Sea in Finland), water entering the car-deck is subject to the free surface effect and may cause a capsize. As a RORO ferry