Looking at the video again (buffers like a bugger), it's hard to tell if one is looking at the bow or the front of the superstructure. What can be seen does not remind me of older WWI subs that I have seen pictures of.
In fact, what would a WWI-era sub be doing up that way if it belonged to any of the major combatants? Did Russia have any at that time?
It still looks too clean to me to have been down very long. Some of the video appeared to show mats of material, but it was hard to tell what that was as there was no frame of reference, nothing to compare it to.