Corrected entry: A squid does not propel itself at speed tentacles first, but head first.
Factual error: When they first arrive on the Nautilus, they look out the large porthole and see the crew on the bottom of the ocean burying one of the crew, but the ocean would be much deeper than that, since the Nautilus is at the surface.
Correction: The first films of giant squid, captured in the Sea of Japan in 2013, show them doing just that. It's all about how they attack prey and the positioning of their eyes, but they can and do travel at speed tentacles first.