I checked my iTunes music library to see if I had a copy of the Gordon Lightfoot song. I didn't. Ninety-nine cents and a quick download later, I did.
The Wikipedia article is really interesting. E.g., the section describing the cause of the wreck also shows that there was controversy with the official reports:
When Fitzgerald first vanished, it was widely believed the ship snapped in half on the surface due to storm action. Precedent surface breakups suggested bow and stern sections would be found miles apart on the lake floor. When underwater surveys revealed these sections mere yards from each other, it was concluded the ship broke when it hit bottom.There's even a link to the official Coast Guard report: MARINE CASUALTY REPORT: SS EDMUND FITZGERALD; SINKING IN LAKE SUPERIOR ON 10 NOVEMBER 1975 WITH LOSS OF LIFE (121 page PDF).
A Coast Guard investigation postulated the accident was caused by ineffective hatch closures. These devices were unable to prevent waves from inundating the cargo hold. The flooding occurred gradually and probably imperceptibly throughout the final day, and finally resulted in a fatal loss of buoyancy and stability, so that the ship plummeted to the bottom without warning.
The Coast Guard report proved controversial. The most common alternate theory contends inoperative radar forced the crew to rely on inaccurate maps. As a result, Fitzgerald ran aground on a shoal without the crew being aware of it and received bottom damage, which caused it to gradually take on water until it sank suddenly in deep water. This theory is supported by final radio communications between Anderson and Fitzgerald. If the hull was indeed breached, it would be difficult to prove. Fitzgerald has settled in mud up to its load marks, making it impossible to inspect for damage.