Drowning

I was on a school bus with a bunch of friends and we were all going to a dance club. We were also in a totally diffrent city, then where we all live. The bus dropped us off and the bus driver told us to call when we were all ready to go. After many many hours at this club, we all decided that it was time to go. We all got on the bus, and I sat in the seat with my older sister. Everyone was still full of energy and all of us were talking and laughing and some were singing. Me and my sister were talking and laughing as well. As the bus was driver was driving over this bridge that was really curvy and crazy winding bridge, that would go up hill and down hill, and was positioned over a large body of water, I thought to myself. The driver was losing control of the bus, and we were about to fall off of the bridge and into the water. I looked at my sister and said , "Oh my god Carol, we are all gonna die." She looked surprised that at me, nobody including my sister, was noticing that we were about to crash into the water. Then suddenly we crashed! Into the water, and all of us screaming and crying for help. We all managed to get out of the bus. I was frantically looking for my sister. We were all treading water and gasping for air. I rememeberd that in my dream, my sister could not swim. (In reality she is a great swimmer.)As I was looking for her, I noticed that the water was not deep at all, it was atleast 4 feet deep. I looked under the water, and found her, trying to get out of the window of the bus. I pulled her out and saved her from drowning. Then we all swam up to the close by shore, towled dried off, and went home. The next day, nobody said anything at all about it, like it had never happened. Please tell me what this means.