I'd like to say once again, what I saw in the video is a bad case of spider wobble.
However, what was DESCRIBED by the OP, is different. He said he couldn't get the "severe" stuff on video ...yet. A snake that is traveling upside down and stays upside down in water without being able to raise itself for 20 minutes, etc etc. I have no seen or heard of a "thriving/doing well" spider be that severe..