This will possibly be a SPOILER for some, so tread carefully.
Gameswire: Here's another boss movie, this time from the end of chapter 3.
What we have here is some sort of sea monster, controlled by a man (we won't say who) strapped to its tongue. Well, not so much strapped, more fused.
Watch in either SD or HD as we make a bit of a pig's ear of this, but manage to just about scrape through at the end.
Also, check out the screenshots from the boss battle via the alternative sources link.