I’ve been in foam that was similar to this (at least by description) and no pfd will have buoyancy that will float you out of it. It’s also less turbulent than

I’ve been in foam that was similar to this (at least by description) and no pfd will have buoyancy that will float you out of it. It’s also less turbulent than the water, so if it were swimmable they would have done it. I expect they were in the surface of the water and engulfed in foam too dense to swim up through and disorienting enough that they couldn’t just head for shore in.