Tampon leaking?


I just started using tampons because my period came during a beach vacation with a friend. At first, I used the smallest size since I had never used a tampon before and wanted to get used to the feeling. I wore one to the beach yesterday so i could swim, but after as I was walking to get some food I noticed some blood going down my legs. It wasn’t much so i wiped it up, walked to the nearest drug store and bought the size up of tampons. I wore one of these during the day when I wasn’t swimming and it lasted me 6 hours, and wasn’t even completely soaked/overflowing. When I tried a regular tampon today at the beach however, after I got out of the water, blood was basically rushing down my legs. It stopped after a little bit while i walked to the bathroom to change. When i took out the tampon, it was completely soaked. I was only there for about 2 hours. How can I fix this? It’s getting really embarrassing.