It was better to choose a conservative swimsuit in high school just now, because you are not particularly old, his defense is not particularly perfect, and you are all classmates and teachers, which is a more formal occasion. After all, I don't go to the seaside by myself. I can wear whatever I like, and it's also a place for class. Just wear something conservative and comfortable. You don't have to care too much about the price, but you don't have to buy anything particularly expensive.