An excerpt from a 1933 article in the journal Nature--imagine seeing a passage like this today:
In the spring of 1933, while Mr. Vincent Astor of New York was cruising among the Galapagos Islands, a specimen of this huge fish was seen and captured...It was swimming at the surface but sounded immediately when harpooned. For an hour and half it towed the launch, weighing about three tons at varying speeds (at times as great as six knots) and mostly in circles. Then it came to the surface and swam about sluggishly for about two and half hours before it succumbed to repeated harpoonings and a number of shots from a heavy rifle. The original harpoon was so firmly driven into its thick hide that it never came out, although it was by the harpoon line that the boat was towed about. Comment was made at the time that the fish offered no resistance and put up no such fight as one would expect from a shark of its size.
The 23 ft. fish was a young specimen.
Source: Gudger, E.W. 1933. A Second Whale Shark, Rhincodon typus, at the Galapagos Islands. Nature 132: 569.
Today, it is prohibited to catch (let alone gun down) whale sharks in Ecuadorian waters. Not even in the name of science.
Basking sharks (also planktivores) used to be common on the west coast of Vancouver Island. That is, until our own government mounted massive steel blades on the front of boats so they could ram them and slice them in half! Now sightings along the west coast are extremely rare.