Hi,
The majority of men’s incontinence swimwear products are designed for light incontinence or bowel incontinence, this is something that should hopefully change in the future!
There are incontinence swimwear shorts available that are designed to hold a heavy pad in place, such as this one: https://www.llmedico.com/netti-combi-aqua-incontinence-swimwear/, which would be worth having a look at!