I'm starting to lean more away from that video showing any marine life or him being taken. I think he just got pulled away by the current and probably drowned or maybe was grabbed by something, later.
Let me offer a bit more of an explanation.
If the end of the video supposedly shows the shark grabbing him... think about it. What are you saying happened? The shark came up from underneath him, grabbed him, then put it in reverse? I don't think that's how a shark works. There are tons of videos of shark attacks of animals on the surface and none of them look like that (that I've seen). Shark swims forward... bites... there would be thrashing, water churning, etc..
Also, people have pointed out that it looks like you can see him emerge again through the netting at the very end of the video.
Most likely... he turned to swim towards the back of the boat where there was a ladder. He couldn't get there and a strong current pulled him off into the darkness before he could be rescued.