Ice bath, cold showers and training adaptation

A while ago on one of the pods, the topic of ice baths came up and (some? all? of) the coaches seemed to have the opinion that ice baths kill gains.
The logic of the always tracked- even if I had a hard time trying to find real data on it when I looked a while ago.
I usually workout in the morning and shower pretty immediately after. Recently, I started doing 30 seconds of cold water at the end of my showers for the longevity/health benefits (thank you Limitless with Chris Hemsworth).
Does anyone know what the time interval of cold needs to be to stunt training adaptation? The 30 seconds is just about enough time to get my entire body to really start feeling cold.