She's the bravest dog on the beach until her paws stop touching the bottom. That's the second everything changes — the paddling gets frantic, her head dips, her eyes go wide.
"She loves the water" turns into "get her out, get her out." And you're already in, shoes and all.
Most dogs don't realize they're in trouble until they already are, because deep water doesn't feel different until she stops being able to rest her legs. By then she's panicking, and panicking dogs sink fast.
WagFloaty's chin-rest holds her head above the surface the whole time — even the moment she realizes she can't touch the ground. So panic never turns into something worse. She floats, catches her breath, and remembers she's got this.