Egypt, on the other hand, is a whole different ball game. It’s easy to recognize this on an intellectual level by reading on Wikipedia. But to see the history laid out like geological stratum is something else: layers on layers of civilization after civilization. Sometimes quite literally, like cases of hieroglyphics covered in multiple layers of graffiti, each layer in a different language.
It’s also enjoyable to see how enthusiastic Egyptians are about this history, and about new discoveries like this one. If you ever get the chance to go, go.
Personally I would love to dive ruins like this, bit the cynic in me knows that tourists would strip the location and ruin it.
You're right that 45m puts of out of range of most divers, but it is definitely still a doable dive with decent divers on twins and a deco stage.
The visibility in the photo looks decent for a silty bottom, I wonder what the current is like since it is in the Nile.
I am also curious about what caused it to become submerged in 45m of water 1500 years ago.
I remember being hooked on the wall and seeing my bubbles descending behind me. That dive felt more like mountain climbing than diving.
One of the divers in my group was already in a mild state of panic and I didn't want to chance them letting go of the wall and descending another 10m.
I had a plan to deal with the current, but oxygen toxicity is another thing entirely.
On the other hand, 45m is totally fair game for technical divers, who are trained in deeper, longer, decompression style diving. Divers who pursue this training need to be tip-top recreational divers first.
The wikipedia page for Heracleion attributes it to "soil liquefaction", i.e. the whole city's underlying soft soil/sand became fluid enough to wash away. It must have been eroded to other parts of the sea, leaving the inerodible stoneworks lying there.