Its probably just me but it looks a bit segmented. Does it have beating cilia? If so it might be Turbellaria species but it might as well be the larval stage of anything
The only movement I could see was slow streching and then a fast shrinking at the same place. I didn't see any forward moving.
The movement was a bit like an amoebe. I have realy no idea wat it is.
I searched a bit at the internet and it could be Turbellaria species but they have all a kind of eye spots witch I don't see at mine. Also not any cilia.