To promote a monster movie, Sony Pictures installed a holographic rig in Tokyo Bay that projects the monster onto a haze of water. What you're seeing in the video wasn't added after the fact—that's actually what it looks like in real life.
The feat uses a water screen (carefully sprayed water jet) and exact light projections to create a giant pseudo-3-D Loch Ness "Water Horse" monster in the bay.

Really a well done piece of advertising and technological demonstrative achievement.