Hey, It's got plastic hoses on the water connections and a switch on the socket-outlet, what more do you want? Gee you people are tough to please. Besides, that flex there would make a rather handy towel hanger.
In many ways, this arrangement is the norm in many "modern" parts of the world. Let me explain ......
First off, having the water heater literally hanging in the shower, as shown, is typical.
Having a switch is also typical .... that is what controls the water heater. That is, if left on, the water heater will ultimately start venting; there is no thermostat. You actually turn the thing on, wait a bit, then take your shower - turning it off as you exit. However, the switch is more commonly mounted on the outside wall of the room, and often has a pilot light, letting you know its' on. Having the switch right next to the heater is a new twist.
As is the receptacle; typically ordinary flex is used (not sealtight).
One detail not obvious in the picture is that the entire service is likely RCD (GFI) protected.
Typically European water heaters are watertight on the electrical part, enough to be mounted directly inside the shower or above the bath tub. In this case they are hard wired though with all other electrical stuff are outside the wet area. The heater itself is probably 220-240V 1500W. The socket and switch inside the shower are close to suicide though...