Though overwash is obviously relevant to ships sinking, specific relevant factors vary considerably between ships and events. Anyone attempting to answer the question would have to know a lot about the construction of this specific ship, as well as have sufficient engineering knowledge to calculate its loading capacity.

Overwash is inevitable, and seagoing vessels must be able to withstand it. If water coming over the bow was enough by itself to sink a ship (as it would be, for example, for a bathtub or most very small craft), then nearly all ships at sea would be sunk in short order.

Seagoing vessels are designed to withstand overwash by being able to have all deckside means of entry to the interior of the vessel securable by watertight closure, and being designed to quickly shed the water over the side so that it does not remain on deck. The problem then comes with how well it does both of those things.

A well-built ship in good condition should be able to withstand complete overwash without breach. However, there is a limit to how much any vessel can withstand, and how many times, and for how long.

Seawater is heavy -- over one tonne per cubic metre. If you get a lot of water on deck, all at once, that puts a great deal of pressure on the hull. If the hull can't take that weight, then a breach will occur. Repeated loading will weaken the hull, so any ship will eventually breach with enough heavy overwash. But it should take a lot more than the worst conditions it was designed for. Such breaches are more prone to occur with older vessels that have more wear, or under unusually bad conditions, or both.

Such was probably what happened to the Edmund Fitzgerald. Forensic evidence strongly suggests that excess topside loading caused one or more hatch covers to buckle, allowing water to enter the large cargo compartments, thus catastrophically compromising her buoyancy when she needed it most. Exactly what caused the excess loading remains a subject of debate, but it seems increasingly likely that she was struck by a chain of rogue waves (the fabled 'three sisters' phenomenon described by many Great Lakes mariners), resulting in already heavy loading being exacerbated by more before the first wave had time to fully wash off.

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