Swimming with le cup

Ok so I have swim practice at 6:00 in the morning before school. When I'm on my period, I usually use a tampon for swimming and then when I get to school, I take out my tampon and whip out my Lena cup to shove up inside me for the rest of the school day. I want to get to the point where I can put in my cup before swim practice in the morning and wear it for the rest of the day. But I’m afraid that when I'm swimming, the cup will like shift around and collect water in it along with the blood making it leak sooner in the day. Has anyone swam with their cup in and left it in after you were done swimming? Were there any problems?