Ancient divers:

Vitruvius connected a long tube of cloth, impregnated with special waxes, with bronze rings every 10 cm to hold the tube open, to a pair of bellows connected to crude cheek valves. This long tube was connected to a mask made of bronze containning a pair of glasses and a checkvalve that allowed air to escape but no water to enter the mask. The diving aparattus was born.

airtube mask

1 - Bronze mask.
2 - Glass vision ports.
3 - Tube connection.
4 - Cheek valve.


What would be the consequences of this on naval warfare? How this could be explored economically? Are there resources underwater that could be taken via divers?

  • $\begingroup$ Just as a note, bronze rings aren't important from a 'structurally open' perspective - your diver and his air will need to be pressurised to his depth. $\endgroup$ – NPSF3000 Mar 24 '15 at 5:10
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    $\begingroup$ In fact the bronze rings would only make the possibility of a fountain of flesh more likely. Under normal working conditions, the tube would be held open by the air pressure inside. When that drops, liquid (and I use that term very loosely) would move up the tube the other way. $\endgroup$ – Aron Mar 24 '15 at 10:33

Be careful with the actual apparatus...you need to ensure that it remains pressurized as well. If the device works:

I cannot see that big of an advantage directly to the military...it's applications for attacking / sabotage seems pretty minimal...if the Romans had explosives that could be transported underwater maybe? But thats not the major benefit I would see.

Your major use here is salvation...the countless number of ships that sank during wars (and peace time for that matter) from military ships to merchants and everything in between are sitting on the bottom of the Mediterranean. Much of the Mediterranean is quite shallow (100 meters?) and this device would allow for large scale salvation operations...sunken treasure much? When Carthage was burned, a fantastic amount of treasure was sunk to the bottom of their harbor...all of which could be recovered by your ancient divers.

  • $\begingroup$ maybe a brace (en.wikipedia.org/wiki/Brace_(tool)) could be used underwater to create holes into enemy ships ? $\endgroup$ – Jorge Aldo Mar 24 '15 at 0:02
  • $\begingroup$ @JorgeAldo I'm sure a brace could make a hole in an enemy ship, but how exactly would that help an attacker? I mean, we're talking about a system that's limited in range, visible to a watchful defense, open to counter attack and slow to execute. I think the payoff would have to be more than a few hand drilled holes that in the scheme of things probably wouldn't even be noticed. $\endgroup$ – NPSF3000 Mar 24 '15 at 9:15
  • $\begingroup$ the idea is to sink the enemy boat by flooding it via multiple holes into the hull. enemy ships could do nothing to prevent underwater soldiers from holing the ship... $\endgroup$ – Jorge Aldo Mar 24 '15 at 15:44
  • $\begingroup$ suppose the enemy fleet is anchored in... lets say... alexandria. instead of a big navall battle, you might take the whole night boring holes into all the enemy ships until they, one by one, sink, without a fight. $\endgroup$ – Jorge Aldo Mar 24 '15 at 15:45
  • $\begingroup$ @JorgeAldo - Took an evening to ponder this, but I'm afraid I need to go with a conditional no. I highly doubt you could effectively sink an entire ship with a hand drill. That said, there is an opportunity to sabotage rudders and steering control...doing that the night before an invasion would have some value, pending how easily the rudders can be repaired. But I think you would be better off if you took the same money/effort needed for this scuba attack and used it to create or arm another ship.I also think the difficulty of working Scuba in blacknees is pretty extreme and comes with risk $\endgroup$ – Twelfth Mar 24 '15 at 17:35

Well, if you're being literal in your description, the first consequence would be a bunch of dead divers.

The problem is in the valve - if it can't 100% reliably withstand the pressure of 5 atmospheres or thereabouts, a failure will lead to excarnation - the diver being squashed into his helmet by water pressure.

You can still get some limited utility, if you don't go too deep, though; having even shallow-water divers (even with diving bells or similar apparata) will help a lot with salvaging ships (and their cargo) if they sank in or near a harbour.

As for warfare, it doesn't help much; you need the pump to stay with (above) the diver at all times, and the diver will be a lot slower than a galley.

  • $\begingroup$ i forgot something. $\endgroup$ – Jorge Aldo Mar 23 '15 at 23:46
  • $\begingroup$ 5 atmospheres is equivalent to over 165 feet (50m) under water, sticking to shallow depths reduces the risk of encountering decompression sickness after an extended dive. Each atmosphere of pressure (14.7psi) is the equivalent of about 33 feet (10m) of water, so the valve would only need to withstand about 15psi of pressure for a diver under 30 feet of water. $\endgroup$ – Johnny Mar 24 '15 at 3:30
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    $\begingroup$ And, since a picture (or at least a Mythbuster's video) is worth a thousand words, youtube.com/watch?v=LEY3fN4N3D8 $\endgroup$ – WhatRoughBeast Mar 24 '15 at 4:23
  • $\begingroup$ Conversely if it could stand 5 atmospheres of pressures and was used as such, you'd likely have a bunch of dead divers. Recreational divers are allowed a whole 8 mins on normal air at 42meters before needing decompression (which they aren't trained to do). $\endgroup$ – NPSF3000 Mar 24 '15 at 5:07
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    $\begingroup$ @MikeL. I'd want to see a source on that, pressure is pressure and the air mix is the same for basic scuba (i.e. normal atmosphere). The movement up and down may be slower than a normal scuba diver... but more than fast enough to skip past a decompression stage. $\endgroup$ – NPSF3000 Mar 24 '15 at 9:10

Romans did not know to make clear glass, or rubber seals, so your divers would dead.

Plus metal was not cheap, even nails considered high technology...

No effect on ship figths, I think. Ship fights happen far out at sea, where divers useless anyway.

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    $\begingroup$ "Colourless glass was produced in the Roman period by adding either antimony or manganese oxide.[1]" from wikipedia article on roman glass. Even if metal is not cheap, i believe the whole empire could afford some bronze rings and masks, they used metal on the soldiers armour (segmentata), why they cant use it on a pair or two of masks ? Regarding rubber seals, you can do with cork. $\endgroup$ – Jorge Aldo Mar 24 '15 at 4:11

If you do not have a compressed air supply:

The suggested drawback of divers hemorrhaging out through mouth and nose because of pressure differential is admittedly colorful and dramatic, but absolutely will not happen if you're not giving the divers compressed air. Reason: diaphragm and intracostal muscles are not strong enough to inflate the lungs against a pressure differential, so your divers will not descend while breathing unless they have compressed air. I know this from personal experience: in my teenaged ignorance I tried to see how deep I could go with an adequately rigid tube. It turned out to be a pretty trivial depth, a few feet IIRC.

If you do provide compressed air:

It's still going to be highly questionable.

The likeliest injury would be air embolism, which is often fatal (and frequently causes brain damage when the victim survives.) This happens when ascending with compressed air in the lungs and (naturally enough, if you haven't been trained otherwise) holding your breath all the way to the surface.

As the air in your lungs expands, it tends to rupture the alveoli and force its way into the bloodstream. Neurological symptoms (up to and including death) are caused by bubbles blocking blood flow to the brain.

The biggest gotcha about air embolism: the maximum expansion happens closest to the surface. In other words, the danger increases as you almost get to to breathable air. :-(

Since the only treatment for this is a hyperbaric chamber, your divers in Roman times would be unlikely to receive treatment. Yes, hyperbaric chambers might well be invented - eventually - to treat the commoner malady of the bends, but it's kind of hard to see the engineering thought progressing like that. Romans were good engineers, no question; but they were not much for theoretical physics. And, since this issue is explained by Boyle's Law, which didn't emerge in our world until the 17th Century CE, you would really need to hack your timeline of scientific discovery...

  • $\begingroup$ A lot of divers would die due to the low tech of the devices, but, Rome was a different world where people died a lot quicker than in our own world. Life was not valued as we value it now. The system would be compressed via the bellows connected to cheek valves, its on the description. $\endgroup$ – Jorge Aldo Mar 24 '15 at 14:25

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