As a woman, I in no way think that a one piece swimsuit is much better than a bikini. Yes it covers more skin. However, it is tight, low cut, usually low back and don't forget the lower half of the suit is just like underwear with regard to the cut and exposure. Both a man and woman's upper leg ... anywhere above knee, should not be exposed and it is very immodest. Even the women's suits that have little skirts are immodest, as the upper thigh is exposed. The only thing I could comfortably wear would be a swimsuit with a rash-guard shirt with short sleeves over the top and long swim trunks (to the knee) over the bottom.
I've seen the modest swimwear offered online ... and that has a skirt type bottom to the knee, with some type of leggings underneath. That's an option too for those who feel more comfortable with that type of coverage.
No matter what you do or what you wear though, getting wet will cause the material to be slicked down against your body ... even the long skirt type things. But with good effort and intention, that would be relatively minor issue.
Now, after we're modestly attired for swimming ... what about sharing the beach or pool area with those who are immodestly dressed ... .? I don't want to see that or be around it .. and don't want to share that environment with H or son.
Annoying because I used to so love swimming. Some of my favorite childhood memories are from summers spent swimming.