AHW, new tube

about a week ago when i went to my boat we bought a brand new lay down tube for our pontoon.  I was the only kid there since my brother was at his friends house. I put on my life jacket and jumped onto the tube. At first my dad went really fast, so i made the sign to go down.  from then on i had a really good time going fast and slow, until i was on it for ten minutes. My dad stopped the boat, and i slid forward and into the freezing water. I couldn't get back on the tube so i held on and went towards the ladder as i was pulled in.