Complete rubbish talk. The drag of swimming on your back in scuba at the angle to keep your mouth out of the water means you’re going nowhere in any kind of a sea. Don’t get separated from the boat or shore you won’t make it in poor conditions if you run out of gas.
If I lost the boat beyond all hope and have to swim for a distant shore, I'm ditching the entire kit and am doing the actual swimming. Including the fins -- but that's just because I'm better at breaststroke than at crawls. If I just need to float waiting for the pickup, then I seem to be intelligent enough to not inhale when submerged. YMM, of course, V.