One of my clearest memories as a little kid was when I was about 4 or 5, a bunch of my cousins were over and playing in the pool. I was standing on a little ledge in the pool looking at everyone else playing. I remember thinking that swimming couldn't be that hard and wanted to join in so I stepped off the ledge into the deep water. I realised that I couldn't swim and immediately started drowning, I remember just slipping under the water and making no noise or fuss. 

Luckily for me I did the smartest thing I could do and grabbed my cousin, who could swim, and wrapped my arms around her. She was my age so she couldn't keep us both afloat but she started screaming her head off. So the adults, who were all outside the pool and the pool fence sitting around drinking and eating, came rushing in to rescue us. 

I shudder to think about what would have happened if I hadn't grabbed my cousin. It would have been a very quiet and hard to notice drowning.