What we even looking at ?
The really small thing i circled?
Even if i zoom in I cant really make it out.
I'm guessing some kind of pod but a closer zoomed in picture would help alot,for others to help you
Edit: ok just down loaded your video,it curls up like an ampripod but to me doesn't move like an ampripod so sorry not much help.
At first I thought maybe a little tiny baby shrimplet but then when curled up thought ampripod,just the colour of head that throwing me off unfortunately