Did a Hugh Williams survive a wreck in Wales yesterday?

"On December 5, 1664, a ship sunk in the Menai Strait, a stretch of water with tremendous tidal swings off the coast of Wales. All 81 passengers died, except one. His name was Hugh Williams.
 On December 5, 1785, another ship sunk in the Menai Strait, with again everyone aboard dying except for one man…named Hugh Williams.
And then again, on December 5, 1820, yet another ship sunk in the Menai Strait. Only one man survived, and he was named Hugh Williams. This is an awesome legend, and the scope of the coincidence is staggering.
Another source actually references two other British shipwrecks with the lone survivors bearing the name Hugh Williams, except they weren’t on December 5. In one of those wrecks, there were actually two survivors, an uncle and nephew, and both were named Hugh Williams. And so despite having two survivors, you could still technically say of the wreck “the only man to survive was named Hugh Williams.”"

Via The Cuttlefish, which suggests that the explanation lies in... mathematics.