In 1991 a ferry called the Salem Express sank in rough weather. 649 on board - 471 died
Thank you - that's the one, though I remember significantly different numbers. And in fact I don't think it was rough weather at the time. The captain was speeding at night and took a shortcut that proved fatal. The ship lodged on top of the reef and people got on with dinner in the belief they would be rescued in the morning and probably wouldn't even get their feet wet. Sadly they were wrong, and the ship slid off into moderately deep water. Most passengers didn't know how to swim - I don't know if it's an Egyptian thing or a Muslim one, but I've rarely come across Egyptians who can swim - and they went down with it. They had had hours to get clear but hadn't bothered.
I've dived it several times from liveaboards (it's a long way out for a day boat), and we always had an unwritten rule on board of "look but don't take anything". Most local dive crews have family members still in the ship, and I've never seen an Egyptian in the water there. They will take tourists as that's how they earn a living, but they will not dive themselves. On one liveaboard I was on someone brought up a child's toy he found lying on the bottom by the wreck, but other divers made him drop it, hopefully before the crew saw it.
As I said, I don't think the weather was bad when the Salem Express went down. I have though been in boats/ships on the Red Sea when storms have blown up, and the speed with which that happens and the severity of the storm is incredible. One liveaboard I was on, the "Tiger Lily", had both an air compressor and a nitrox compressor bolted to the deck in the wet area, and the ship was all steel. The storm was so bad one of these compressors tore up the section of deck it was fixed to and disappeared over the side, and the other was severely damaged. We limped back to port with engine room damage as well. If a ship breaks up there in a storm it is completely unsurvivable. I have been in storms on other seas/oceans, and nothing comes close to Red Sea ferocity.