When is it okay to bring LO to swim? Need thermal swimwear? Waterproof diapers? Where to get it? Thanks

Hi how old is ur lo. I brought my girl to babyspa when she around 3month. But is always to get a trial session to try out first before buying a package as it not cheap and some lo dont like. I only brought her to public swimmimg pool when she is 1. For diapers i bought whichever is having promo like huggis n pampers that can be find at ntuc. A washable swimimg pant will be more worth us it reuseable .