(YouTube link)
The moral of the story is: if you are going to sail off the coast of Wales on December 5th, you may want to change your name to Hugh Williams. But is this a true story? Any records from these incidences seem to be at least second-hand. I found a post at The Scuttlefish that may shed a bit of light on how "coincidental" the story really is. And be sure to check out the comment from Hugh Williams. Link
I'm not convinced by the author's incredibly limited research. For example he confidently states that the name Hugh in Welsh would be spelled Hew. I think you'll find it's Huw.
Most likely it has some basis in truth which has since been somewhat embroidered. Men named Hugh Williams being among the survivors of, say, three shipwrecks is something of a coincidence but doesn't make a great myth. OTOH if you amend the story to make Hugh the sole survivor then that gives the story more of a kick. Make the wrecks happen on the same date and add a few more wrecks and your story will grow legs.
Believe it or not, all three Hugh Williams and I have different mothers together.
Hugh (Hew/Huw etc) is a very common Welsh given name.
Williams is the second most common Welsh family name.
It is very unlikely that there would be no wrecks in the Menai Strait's huge catalogue of disasters that could be grouped like this!