You're right. Mulberry A did deploy briefly before being destroyed. I recently read about a piece of Mulberry still in a bay in England. It was destined for Omaha, but sank before they could tow it across the channel.

The confusion comes from the fact that “mulberrys” is commonly used to describe both the building blocks of the harbors and the harbors themselves. The giant concrete “floating” caissons were constructed off English ports, partially sunk (to keep them out of German aviators’ sight as much as possible), refloated and towed across the Channel and then assembled like giant Lego blocks to form deep water harbors.

Most of the caissons were actually used as “breakers”, to lessen the wave action of the seas, and there were more than 400 such caissons in all. It’s not surprising that a few might have sunk along the way, or even not been able to be properly refloated once the order came to do so.

The logistics must have been a nightmare; building them, getting them out of the way so more could be built, then refloating them, towing them across the Channel, and then sinking them in place to form the harbors, such as they were. And then constructing the infrastructure to allow smaller ships to offload and transport the goods to shore.

Daunting. I have read that in spite of the Allies attempts to keep them secret the Germans knew of them but couldn’t figure out what they were for. Only a small fraction were visible at any time, so the scope of the project never came to light until June 6. Perhaps the Germans thought the Allies were trying to construct cement boats or something? Odd, the things that go on in a war of deception and intrigue.