^ Yeah, but I just make it look glamorous. You don't see all the boring parts.
Anyway... moving on from passport renewals and trips to Bangkok...
Well Ootai, now that I've got used to sharing the boat with a load of new people and am learning to cope with socialising again, I've had time to look into your question.
From what I can gather...
The Dardanelles and Sea of Mamara were formed millions of years ago by crustal movements and comprised part of the Aegean during pre-history. The Black Sea was originally a freshwater lake, well below sea level but cut off from the Mediterranean by a piece of land that included the Bosphorus Valley.
Around 7000 years ago the rising Mediterranean (caused by melting ice at the end of Northern Hemisphere glaciation) formed a channel through the Bosphorus Valley and seawater flooded through to inundate the Black Sea. It has been estimated that the volume of seawater pouring through was 200 times the volume of the Niagra Falls.
The Black Sea is thought to have widened by up to a mile a day during the deluge, burying the shoreline beneath hundreds of metres of salty seawater.
This flooding of the Black Sea has been linked to the story of Noah’s ark, which traditionally is thought to have come to rest on Mount Ararat in Turkey.
At present day, denser, more saline water from the Aegean flows into the Black Sea underneath the less dense fresher water that flows out. This creates a significant and permanent layer of deep water that does not drain or mix, and is therefore anoxic (no oxygen).
Below 150 metres water depth the Black Sea is anoxic and lifeless and the seabed across the Abyssal Plain (typically around 2200 metres depth) consists of a foul-smelling sulphurous sludge which is completely devoid of life. The water quality isn’t helped by the sea being surrounded by some of the most polluting nations on the planet, and what life the Black Sea does sustain in the shallower, oxygenated water is under threat from pollution and over fishing.
Anyway, what effect does all this have on us?
From 130m depth the Black Sea water contains Hydrogen Sulphide (H2S), which increases in concentration with depth down to 2200m. Within the deepest areas the concentration of H2S can be 12ml/l, or 1.2%. This means that at the end of every dive the ROV has to be hosed down before being brought to deck.
As I’ve mentioned before, everything comes down to geology!