A thick seal around the side of the phone, which makes it thicker than the regular version, could be a hint that the phone on the video is the Galaxy S5 Active. While the regular version of the phone has IP67 certification, the Galaxy S5 Active is rumored to have IP68 certification which means that it can be submerged in up to 5 feet of water for as long as 60 minutes. Perhaps a tighter seal is required to hit that level of water proofing. The back cover is aluminum, and the phone came "out of the wrapper" with the Google Now launcher.
Check out this mystery by clicking on the video below.
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UPDATE: A follow-up video from the same source revealed far too many inconsistencies. While the model number on the phone did show the SM-G906 belonging to the Samsung Galaxy S5 Prime, the screen's resolution is only 1080 x 1920. In addition, the 480ppi reading would indicate a sub 5 inch screen. And the chip inside is the Snapdragon 800.
Conclusion? This is not the Samsung Galaxy S5 Prime, nor is it the Samsung Galaxy S5 Active.