Except there weren't any animal cruelty on the movie.
The videos aren't even taken on the same shoot. When the dog was not comfortable with the stunt they called it off to re-shoot when he was comfortable. They resumed the shoot later when he was ready for it and no longer afraid and that's when he went under, was immediately rescued, and is 100% fine.
This is according to the studio, but is supported by the fact that the handler clearly doesn't want the dog to enter the pool before he's calm, and that a significant piece of footage is suspiciously missing in between the two cuts which corroborates that this was two separate shots and that the dog was not allowed into the pool until he had been properly acclimated.
This could be entirely wrong and all PR bullshit, but seeing as a 5 year-old could tell this video is edited and TMZ currently controls it, I'm making the logical assumption that they edited it to support whatever agenda that would get them the most coverage cutting out something that would have disagreed with it. Crucial footage is clearly missing, and if it supported their claim they surely would have included it and there would be no need for the heavy-handed editing. The other possibility is that the person that leaked the video edited it beforehand so that it would be considered more valuable to TMZ, and TMZ just didn't care.