Possible Clues:

• Take the top off this water and you're left with the result of 19 across
• Body of water bounding Russia etc. - sounds murky
• Slab cake (anag)
• Eternally
• Where the water is dark enough to be without water at last
• Crimea a peninsula in it
• Tideless expanse of water between Russia, Ukraine etc - sounds murky
• When Abe is around, this is without the dark water
• When Abe is around he is without the dark water there
• What lies north of the Bosphorus