That dam was many millions of years ago.
According to AI which did the research:
The Atlantic Ocean last breached the Strait of Gibraltar and filled the Mediterranean Sea approximately 5.33 million years ago, in an event known as the Zanclean flood. This cataclysmic event marked the end of the Messinian Salinity Crisis, a period during which the Mediterranean basin had partially dried up due to the closure of the Atlantic-Mediterranean gateway.
The flood began as a small trickle when the land bridge at Gibraltar started to subside. Over several thousand years, this trickle grew into a massive torrent as water eroded the channel, eventually reaching an estimated flow rate of up to 100 million cubic meters per second. This enormous influx of water raised the Mediterranean’s level by up to 10 meters per day at its peak.
The refilling of the Mediterranean basin was remarkably rapid:
Up to 90% of the refilling occurred in less than 2 years, possibly even within a few months.
The flood carved a 200-kilometer-long channel through the center of the Strait of Gibraltar.
Global sea levels dropped by 10 meters as the Mediterranean filled up.
This event is considered the most abrupt global-scale environmental shift since the extinction of the dinosaurs. It not only refilled the Mediterranean but also transformed the regional climate and ecology, effectively “rebirthing” the Mediterranean Sea
>>That dam was many millions of years ago.
there is also a theory put forward by Paulino Zamarro of a more recent land bridge (possibly due to silting in the channel) based on references in ancient writers (Seneca, Diodorus Siculus, Strabo). The timing of the breach varies from 9,000 B.C. to 400 B.C.
Also, see:
https://freerepublic.com/focus/news/601935/posts
This event is considered the most abrupt global-scale environmental shift since the extinction of the dinosaurs.
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Other than the massive comet debris bombardment in 10,900 BC which burned off 10% of the Earth’s vegetation (and a lot of oxygen), ushered in the 1,000 yearlong Younger Dryas Event - the coldest period recorded, caused the Ice Cap to fully melt, raising the sea level worldwide 400 feet, and caused the extinction of the Mega Fauna (woolly mammoths etc).
Other than that, nothing happened.