purchase a waterproof 45mm band

Hello 93upperwestside,

This Apple Support Article will help answer your question. Pay special attention to the section titled "Apple Watch Series 2 and newer". It provides instructions on how to use the digital crown to assist in removing any water inside the watch.

About Apple Watch water resistance - Apple Support

not sure if any of the bands take damage from water but some like velcro or ones with magnetism may be a poor fit for swimming.