Yeast infection

I went to the beach & I was in the water for about 40 mins & some sand always gets around my butt crack but I did clean myself at the sprinkler. Not inside my vagina but I tried to rinse off as much sand off my body as I could. Me & my bf had a quickie afterwards who was also in the water with me idk if he had sand on his dick or not but I did take a shower about 3 hours later when I got home. Anyway my butt was itching like closer towards my vagina it felt like a little rash or well bumps & I put some ointment on it (not on my vagina) but my vagina has been feeling a little itchy not really the inside but it felt irritated so I put Mobistat in right away and this is when I feel like it’s rlly starting to itch but has anyone else got a yeast infection from the beach?