On average about 500,000 per year.
None
See How_many_times_a_year_do_ships_sink
3
Roughly 2,000 merchant ships in WWII.
3,000 Allied ships (175 warships; 2,825 merchant ships)
Primarily over 2,000 merchant vessels, with a sprinkling of allied warships.
The Sussex Pledge (:
The tactic began in WWI and is known as Unrestricted Submarine Warfare.
Ships do sink....
Uboats were made to attack and sink merchant ships carrying supplies to Great Britain. Germany knew if they managed to cut Britain's supplies off then they would be unable to continue the war. They did this by launching torpedos which blew holes in enemy ships under the waterline, causing them to take on water and sink. As the war progressed, more and more were built to combat military ships as well as merchant vessels. Hope this helps.
There is no exact number, and you don't have to sink all the ships, only Captain Crawfish's ship. You need to buy a Phoenix Warbird to sink it.
German U-boats were used to sink mainly merchant ships, so as to starve Britain of food supplies and ammunition.
The Merrimac sunk 2 ships in the Hampton Roads.