Is it normal to wear boxers under swim trunks?
Depends.It depends
Yes, some people wear boxers under swim trunks, especially if the trunks don’t have a liner. Regular cotton boxers can get soggy and uncomfortable, though, so swimwear made for the water is usually a better choice.
It’s a personal preference, not a swimsuit rule. If your trunks have a built-in mesh liner, most people skip the extra layer. If they don’t, wearing something underneath for coverage or comfort is common enough.
The main downside is that ordinary boxers can soak up water, sag, and take ages to dry. If you want an extra layer, quick-drying swim briefs or compression shorts are more comfortable than cotton boxers.