Plesiosaurus/nessie's tail, somewhere between 0:09-0:11. It's like 8 frames.
Anyway, another peaceful day under the sea. Goddamn, Kaku Choushi's works are god-tier. There just so many details to keep you entertained; Warusame blasting off like Zeong, the adorable PT troupe following a Chi-class, Re's antics, and mostly, that adorable Hoppo.
Also, is that Isolated demon or Isolated princess? She's sporting a cleavage on her outfit. Edit: By the way, the book she sneaked seems to have "薄" on it. Any guess as to what it is? Nevermind. Thin. As in thin book.
I love how all of these have so much going on. It's fun to discover all the little actions in the background as well as the "main" actions. kaku choushi is so awesome.