Help girls only piriod at shoool problem?

So we do this swimming thing at the beach an I know I have to wear a tampon (tho I can't get it in and I don't really want to ask my mum for a lubricant ) but I get to school at 7:45 (I would all ready have it in but the swimming thing dosent finish in till nearly 11:00 am so I kinda wana have it out if you no what I'm mean but we all so have showers and they don't have doors so no one takes there bathers off but I wantto take the tampon out then but I have a heavy flow and would not have any time to get in my pants and pad on be for blood would be running down my leg I could take it out in the bathroom but I would have to get changed in the change room and there's no were to go and ever one would see the the string( there all perverts) help on any to do with my problem xxxxx mia