I do think the ships were in the strait, that's what several articles appear to imply. Only, the oil spreads because of the currents between the Azov and Black seas.From the map on the above link, it looks like a fairly narrow strait. It's hard to find information about exactly where the ships were (inside the strait/outside?). If they where actually inside the strait, it's easy to understand why they were damaged/sunk as they were.
Anyway, I haven't found enough details, and I'm tired of looking, to figure out where each damaged/sank ship was, and why they chose to stay in or around the strait, rather than head out to the Black Sea in an attempt to avoid or ride out the storm.
Why were they in that strait, rather than in harbour or at open sea? Yeah, that's exactly the question I guess.