Floating and sinking

Today we went down the pool to test my boat with my class my teacher filled my boat with water so it was more dents. when we got down to the pool i got told to put it in it started to sink but the only bit that floated was was the top caps of the bottle because it had a little bit of air at the top we pulled it out then put it in for another test then it started to roll over then the bottom started to be the top then we went back to class and put the boat up.