It is OK to share a shower with your teammate.  It saves water. It is OK to help him wash his back. As you lather up his back, some of the soap will naturally fall down and cause your rigid boner to get covered with suds.  That is OK too, as it will help lubricate the insertion.  As you slowly force your thick cock into his ass, he will moan loudly, that is also OK, since the rest of the team can already clearly see you raping him thru the glass shower doors.  And finally, it is OK to cum in him, since it will make it easier for the rest of the team to slide their cocks into his tight ass if it is filled with a warm, slick wad of jock jizz.