Based on how dolphins are observed in the ocean...
"now you see us, now you don't"
A sloppy and easy to spot team trails a suspect, gets noticed, and then after awhile, they stop pursuing the suspect. The suspect realizes that the people spying on him have stopped, and then gets a false sense of security.
It would be as if the people tailing you had left you for a picnic. (or so you think...)
But instead of the sloppy team tailing the suspect, a new upscaled professional team moves in to do surveillance, with precision and fixed posts.
David: Yes, but now they aren't anywhere to be seen... It's like they dissapeared on us.
Jon: Diana told me about this, it's dolphin surveillance!