Is an electrical cable allowed under the shower?

Then just take a photo of your situation. In any case, there is an area in the shower, where you stand to shower, where no cable is allowed to lie. A defined hand area is specified there. Maybe that's where the problem lies and the other electrician is correct with his statement.

These long-haired people with dark clothes [dunklen Haaren] and fair skin are creepy to me. But the idea behind it is nice.

Hi,
is VDE compliant. Cables under plaster may run along the shower at any time. Non-compliant would be a tapping point 60cm around Zone Zero (light or socket).
Short quote from the regulation:

Cables and wiring systems may be installed in a residual wall thickness of less than 6cm if
a: the circuits are SELV, PELV, protective separation OR protected by a 30mA RCD and contain a protective conductor.

So, no problem at all. NYM has a protective conductor and RCD is mandatory anyway.

Riddle hour???

Then just take a photo of your situation.
In any case, there is an area in the shower, where you stand to shower, where no cable is allowed to lie. A defined hand area is specified there.
Maybe that’s where the problem lies, and the other electrician is right with his statement.

I’m happy to do that, but it’s actually easy to understand, isn’t it?

The cable lies on the sole.

Then it goes toward the shower through the shower tray, if I had one, and then up to head height, then out into the garden.

Hi, it is VDE compliant. Cables under plaster may run along the shower at any time. Not compliant would be a tapping point 60cm around Zone Zero (light or socket). A short quote from the regulation: Cables and wiring systems may be installed in a remaining wall thickness of less than 6cm if a: the circuits are SELV, PELV, protective separation OR protected by a 30mA RCD and contain a protective conductor. So no problem at all. NYM has a protective conductor and RCD is mandatory anyway.

So less than 6 cm is also okay in Zone 0? I only get 3 cm with plaster and tiles. It's clear at the bottom, as there is still screed etc., total about 20 cm with insulation.