The list of things that can't be deep fried is very short—and water isn't on it, according to the clip above.
YouTuber Jonathan Marcus takes a large water droplet, dips it into flour and panko bread crumbs, and then gently places it into a deep fryer. The result is a fried ball, that the chef cuts open to reveal a liquid that he then consumes. But those who bother to read the video caption will see that the crucial part of this experiment happened before the camera was even rolling.
The ingredients listed are water, flour, egg, panko, peanut oil heated to 375 degrees, and maybe the most important addition, calcium alginate. The gelatinous substance is made by adding calcium chloride to sodium alginate, which is commonly used in molecular gastronomy for food spherification. The calcium alginate surrounds substances—like the water in this video—with a membrane that allows them to hold a shape. The method used in this experiment is called frozen reverse spherication, which involves freezing a "calcium mixture" before submerging it into the alginate.
The membrane holds the water inside and the breading allows it to be deep-fryable, completing the edible illusion. (As the video warns, you should definitely not try this at home. If the membrane were to burst and release the water into the hot oil, it could cause serious injury.)