NO! Don't do it! Diaper covers are laminated to be water resistant which means they work great at keeping wetness in when used over a fitted or prefold cloth diaper. If you use this same material in the swimming pool, any water that gets into the diaper will be squished out through the leg holes. So, imagine if baby poops! Unless it's specially designed with snug fitting elastics, you end up with poop coming out at the legs. Yuck. This is exactly what the pool doesn't want.
So what's the difference with a cloth swim diaper? It looks just the same as a cloth diaper cover. Well, yes, it might look similar, but the difference is that there is no lamination on it. It's the same knitted polyester fabric on the outside, but most are not laminated with PUL or TPU. It's instead lined usually with mesh. That means it lets some water through and acts more like a strainer to let water through and keep solids in without forcing poop out near the leg elastics. That makes a huge difference in functionality.
Swim diapers are not expensive and are well worth getting. They are specifically designed for the job at hand and usually also sport special elastic that won't be weakened by the chlorine in the pool. The only time you can use a diaper cover as a swim diaper is if it's delaminated and you peel the lamination off first. Plus take extra care to make sure you have snug fitting elastics at the waist and legs with no gaps. Otherwise, just get a swim diaper.
Don't be that baby that shuts down the pool from a poo'splosion 😉. Get a swim diaper here. And while you're at it, take 10% off any swim diaper coupon code: SWIMBLOG