At the 2:03 mark in this clip there clearly appears to be a man with facial hair inside the mouth of the fish. This clip is from the original "Blue Planet" documentary series. I was just watching it on Netflix and noticed. A couple people mention it in the comments, but it never gets any traction.
I don't see hitler this guy has more facial hair. Watching the entire episode I notice lots of cheap looking CGI effects. I am doubting the whole Attenborough documentary series now.
A couple people I showed this to think it might be some sort of reflection. Most solid theory I have heard yet, but this is still unsettling.