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Comment by nradov | Hacker News Reader

Some sensitive areas have had good results with requiring tourists to dive with licensed local guides. But 45m is a little deeper than most recreational divers can safely go. To do it safely and get a reasonable bottom time takes some basic technical dive training plus double tanks with normoxic trimix, and a decompression stage. (I know many divers have gone deeper using a single tank with compressed air but if anything goes wrong it can turn deadly in seconds.)

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My deepest dive on a single tank was 57m, and I wouldn't recommend that or try to repeat it. Down currents can be terrifying.

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.

57m on a single tank would just be so short too; air goes quick at that depth, and the longer you stay down the longer you have to take getting up.

it was definitely not the plan.

I remember being hooked on the wall and seeing my bubbles descending behind me. That dive felt more like mountain climbing than diving.

Some walls have vicious down currents, but if you just swim away from the wall a few meters the current will decline and you can establish positive buoyancy.

You're right, but I wasn't willing to take that risk.

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.

Oxygen toxicity isn't really a factor at that depth; you'd run out of air on a single tank before experiencing any toxicity symptoms. The immediate concerns would be narcosis and hypercapnia.

Climate change?

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