Turns out, theses dolphins aren't really in on the joke. According to Ric O'Barry, founder of the Dolphin Project and star of the 2009 film "The Cove," staying still like this is something dolphins are frequently coerced to do in captive settings, like while awaiting a command.
"The dolphins in this video are performing an unnatural trained behavior called 'stationing,'" O'Barry told The Dodo. "The dolphins do this for a food reward. All of the dolphin trainers in the video are simply participating in cheesy publicity stunt, at the dolphins' expense."