That close-up that you showed,
Backfromthedead
, was the one individual that had me really unsure at first. Then when looking at a couple of others, that arrowhead-shape and a set of eyes almost sorta kinda seemed to be there...but the inchworm-type motion clinched it for me. I've never seen planaria do anything other than the smooth glide.
But now I see that underwater video and there does seem to be some gliding going on there, which says no to leeches. The original video is gone now?
If they're planaria...well, those are big-ass planaria! I've never seen them approach that size, but I'm sure they get bigger than the ones I've seen.
I'm still leaning towards leeches, but...I really do think we need to wait for the taste test.