Roman diving helmets?

So if these 'gladiator' helmets were actually stylised versions of 'diving' helmets, how might a Roman diving helmet work? To be honest we have only hints. For one, we know divers were nicknamed 'Urinatores' - I'm pretty sure I don't need to supply a translation for that. It's generally accepted the term arose from divers using air-inflated animal bladders as buoyancy devices - these would allow a diver weighted with stones to dive to a greater depth and return to the surface faster when the stone weights were removed. But that's the accepted thinking. We know the larger diving bells the Romans used for underwater engineering could be fed by air pumped from the surface, which suggests that the Romans had a reasonable idea of pneumatic forces just as they understood hydraulics. So let's look at it this way. A Roman diver, wearing an air-filled helmet is standing on the sea-floor with pressurised bladders filled with air - could these have been connected to the helmet to equalise pressure and various depths and to supply several minutes of breathable air underwater? Modern bronze taps, spring-loaded pressure valves and piping were all available in the Roman tool-box - so methods to control the flow and storage of air in bladders and helmets was possible. But most of all, remember, there was an economic imperative to harvest half-a-billion sea sponges every year - an imperative that required someone to figure out how to maximise dive times and exploit as much of the seabed as possible. Roman diving helmets might be something we haven't heard of, but they shouldn't be something we should dismiss as impossible. If you want to read more about Roman diving helmets - check out a 'Body of Doubt' - live on Amazon now or on YouTube