I'm like you Arimeh, I leave the 2 older boys in the bath on their own. They make that much noise and mess that you know what they are up too. I stay in the bathroom whilst my youngest is in the bath as I don't trust them at all with him, and I too agree they would have enough thought due to their age to do something if he went under (well not quickly enough) but I then generally get DS3 out and take him to the get dressed whilst the older two then have fun. They don't have deep baths and they have done swimming lessons since they were little so I know they are familiar with water.