I think the numbers of sunken ships is reasonable. In the age of sail wooden ships were much smaller than freighters today. A typical Spanish galleon was 100-150 feet (30-45 m) in length and 40-50 feet (12-15 m) wide (the preferred ratio was 3:1 or 4:1). If you have smaller ships you have to have more of them to move cargo.
Also sailing ships depended on the wind to move and often the wind, even without a storm, would remorselessly drive these ships onto rocky shores to break up and sink despite all efforts of the sailors. Sailors called shores where conditions were likely to drive their ship onto the land a lee shore.
A lee shore, sometimes also called a leeward (/ˈljuːərd/ shore, or more commonly /ˈliːwərd/), is a nautical term to describe a stretch of shoreline that is to the lee side of a vessel—meaning the wind is blowing towards land. Its opposite, the shore on the windward side of the vessel, is called the weather or windward shore (/ˈwɪnərd/ or, more commonly, /ˈwɪndwərd/).
Because of the danger of being driven aground on a lee shore it is essential seamanship to treat one with caution. This is particularly the case with sailing vessels, but a lee shore is an issue for powered vessels as well.
dayglored has a point, the math seems to not add up and I question it too. But to support your argument also I think there is another factor. I’m sure they were not all treasure ships. I’m sure the bulk of them were large daily fishing vessels labeled as ships. And there were a LOT of those... They were probably built in many locations simultaneously dozen or more a month.
Back then at lot of songs and poems were written about sailors going to sea and never returning. So I’m thinking it was pretty common. Sailing was a risky business and every time they went out they said their last goodbyes in case they never returned because it was so common.
Every trip out it was a really big deal when a ship actually returned back to port. With that said I wonder how many viking ships are on the floor between Scandinavia, Iceland, Greenland, and in the North Sea? Fishing vessels included bet there are several thousand at least. The North Sea is brutal...
That made me think of Horatio Hornblower's first lieutenancy exam...there's always shoals to leeward in a lieutenancy exam apparently.
“...Because of the danger of being driven aground on a LEE shore”...
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To a casual observer, the LEE shore is the shoreline in the calmer “shadow” of the wind.
Once on board and driven against the rocks, it becomes THEIR lee shore.