The longest containers you typically see are 45 feet, though Wikipedia says they come in sizes up to 56. The item in the photo is 79 feet long. It could be a wing at 79 feet - or it could be a photographic artifact or a blasted whale. Won’t know until they find something. The suspense is killing m . . . zzzzz.
I am no satellite photo analyst, but the more I look at it the more I see the sun reflecting off the face of a large wave or the white foam from a breaking wave. I hope they had multiple frames showing this item in different positions before they told the world they had something. I see about 10 similar reflections in the photo that has been distributed.