Exactly what @JonaO703 said, the little floaties were already a separate accessory in Island Living and I expected them to function this way.
For those who wish to wear the floaties to a pool but remove them from a sunbathing sim, I suggest saving two different swimmwear outfits (yeah, that is a feature, you can create multiple outfits for each category) and click "change outfit" before switching before activities to make them nicer for photos, videos or just immersive gameplay. Unfortunately this does not remove the fact the floaties don't work with all swimwear, though.