Oh, and one tip we got that has been pretty effective is to give him some sort of buzzer, whistle, bell, etc. to use to contact us should he be in danger. We let our DS pick out his call tool so we have a bicycle horn sitting on the back of the toilet. At first he would use it to call us because he felt scared but we reinforced that it was for dangerous situations and we let him sort of play with it while we were there - ie a few fun honks. He has not touched it now in a few weeks.