best swim diapers for a 13lbs baby?

I use pamper's splashers

All swim diapers go by small, medium or large sizes. So your baby will be in a small.

the small ones start at 16lbs @valerie_jean

babyganics swim diapers, i love them

You'd still want to put him in a small lol

I think pampers does actual diaper sizes like 1-2, 3-4, etc.