HELP! School trip to water-park?

My school is going on a trip to Six Flags: Great Escape tomorrow. However, I wanna go to the water-park area and I'm on my period. I know I should wear a tampon, but should I wear a panty-liner, too? My bikini is light-blue and white and I'm afraid I'll get blood on it and it will show through. I have shorts I can wear, but they aren't very comfy. Help!!!