May one think of Drivre Torah in the shower?
From the verse (Devarim 23:15) “Ve Lo Yirae Becha Ervat Davar,” it is learned that one may not say any words of Torah in the presence of one’s own or another naked body. This prohibition, however, only applies to uttering words of Torah, but not to thinking of them. Accordingly, the Mishna Berura (M.B., O.H. 75:29) rules that if one is naked, such as in the shower or in the Mikve, one may contemplate Divre Torah. Additionally, Rabbi Ovadia Yosef (Halichot Olam, vol. I, pg. 119) one may listen to Divre Torah while in the shower, so long as the shower is enclosed and separate from the bathroom, especially in light of the fact that nowadays, showers are considered to be clean areas. It should be noted that one may not even think of Divre Torah in a bathroom. The Kaf HaHaim (K.H., O.H. 75:28) writes that one may recite Vidui while naked in a Mikve without mentioning Hashem’s Name, and this is a common practice on the eve of Yom Kippur.
Regarding answering “Amen” to a blessing in which one wishes to be included, the concept of Shome’a Ke’One states that by answering “Amen” it is similar to one actually saying the blessing, and this is not permitted in the shower or Mikve. If one hears a blessing in which one does not want to be included. Furthermore, even If one hears a blessing in which one does not want to be included, by responding “Amen” one is affirming the blessing and in a certain sense it is as though one is reciting it oneself. Therefore, even for this type of blessing one is not permitted to respond “Amen”.
Summary: One may listen to or think of Divre Torah in the shower or Mikve. One may not respond “Amen” to a blessing while in the shower.