Of bridges.

They all say that the bridge collapsed between Russia and Krimea due to a truck full of explosives, but personally I have doubts. I'll show below the video with my doubts. And it is important that small boat that can be seen appearing, on the right below, under the bridge before the explosion.

If you can't read it, the video is here:

As you can see in the slowed-down images, just before the bang (a couple of seconds) at the bottom right you can see a small boat peeking out from under the bridge. And that explains why it collapsed.

Concrete is an ugly beast to blow up, and a bridge this big can't jump for a single truck of explosives. The one that collapsed in Bologna was a simple overpass, which holds up to 30psi, but that bridge there was much more robust. More was needed, explosives.

What does it mean?

More or less it means that the Russian navy really fails to protect Crimea.

And here are problems.