Cylinder below airplane, moving faster than us to our left about 30 degrees off of our heading

While watching the ocean below I saw a gray cylinder. There were no wings, nothing that I could see on it, no exhaust. It occurred to me that it was something strange, so I called to my husband, who leaned over to look out of my window and I asked him “What is that” and he said “I don’t know”. It was headed for a tall cloud bank, and we both saw a shadow from the cloud bank fall over it before it disappeared into the cloud, where we lost sight of it.