period whilst on holiday😨

In august I'm going on holiday twice in the same month. One with my dad and one with my mum. I'm terrified that I might start my period whilst I'm on holiday with my dad, because obviously he's a man and he won't understand. I feel more comfortable being around my mum when I'm in my period. But if I do come on my period whilst I'm with my dad what do I do? If I'm with my mum I can just tell her that I can't go swimming etc. But with my dad I can't. Any ideas on what to do?!?