As Salaam Alaikum
I came across a video clip for performing wajib ghusl in a shower.
In western life styles, we normally stand in shower and perform ghusl after cleaning body.
The video clip mentions that after wahing head and neck and before continuing with ghusl on right side of body, its important to step out of shower.
Normally this will cause whole bathroom to get wet and also half of ure body is still najis and half is pure.
Please describe how to perform ghusl in shower as per my Marja

Standing in shower is not correct method of ghusl
Because your ghusl is tarteebi which suppose to be perform in order .
First remove the Najasat then do the niyat of the ghusl and first wash your head and neck then right part from shoulder to foot then wash left from shoulder to foot . This is the ruling you may see in tauzeehul Masayel also