Shower together

Sorry for the intimate question, but I saw it on the Treasury of Wisdom forum:
And so many guides – also from the Hasidic sector – but mainly in Lithuania advise couples to shower together and of course they will not write it in writing and only verbally because it is a very open line, I personally, until I heard it firsthand that it was like that, I did not believe it. He added that today in recent years there are guides, especially in the Lithuanian public, who advise this from the outset and not as a solution to the problem, but that this is how they will behave from the outset – and in the first year, and again, I heard this firsthand from a Hasidic groomsman guide in Bnei Brak.
What does the halacha say, and what is the rabbi's opinion on this?