Feasibility of body armour for mer-people

Question

I have seen a number of posts on this site about the difficulties of technological advancements for those who dwell beneath the surface of the sea, and this is colouring my treatment of mer-people in my story.

My mer-people look like a human with a cetacean-like tail in place of their legs. They can breathe both air and water. When breathing water, they take in water through the nose and mouth, and eject water through gill slits on the sides of the chest, between the ribs. When breathing air, they close their gill slits and breathe in the manner of land-dwelling mammals. Merfolk are capable of altering their buoyancy in water. They do not spend more than a few hours out of water at a time, and must use their arms to move effectively on land.

I have been considered what sort of body armour might be made by people whose only access to metal might be via occasional trade with surface dwellers, and whose native technology is neolithic, and whose warfare is similarly primitive.

The first type of armour I have considered would be made from the bones of sea mammals such as whales, as well as whale baleen, fashioned into plates and joined together with natural fibers.

The second type is similar to the first, save that it would be made from abalone shell, which is known for its impact resistance, and could be polished as an artistic statement, as well as being protective.

These would both be varieties of lamellar armour.

How feasible would these types of armour be? Please consider factors such as the ease of manufacture of each type and effectiveness against primitive weapons such as spears and knives, as well as the natural weapons of large, dangerous, aggressive sea creatures such as sharks?

Answer 1

Firstly, you should probably forget about trying to protect yourself from large predators like sharks using armor. Things live in the sea that can eat crabs and turtles and have the jaws and dentition to back it up; you're not going to be able to cobble together good enough armor to defend yourself against those sorts of things, and anything with small enough teeth that you can easily ward it off with bits of stone and shell and plant is not going to be much of a threat to you in the first place.

Secondly, you only really have to worry about two kinds of weapons... pointy polearms, and small knives. Swinging swords and axes underwater is pointless and futile, and projectile weapons are both hard to make and even when you can make them they'll be pitifully short ranged. Knives are used at close range when you can actually grapple with your opponent, and finding the gaps in primitive armor to stick a blade through is probably not going to be very challenging.

Thirdly, everyone always gets too hung up on armor, and forgets about shields. They're much easier to make and pretty effective against a whole range of attacks in a way that primitive armor can't ever be. They also don't need to be nearly as protective as armor, as having someone stick a spear through your shield is less bad than having someone stick a spear through your chest, for example.

Fourthly, combat between tail-using swimmers is going to be a bit different to combat between bipedal walkers. There's a much smaller cross-section of your opponent exposed to you... either head/shoulders if they're coming towards you, or the tail if they're moving away from you.

Lastly, stuff rots fast in the sea. By definition, it is always wet, and readily accessible to any microbe or planktonic scavenger that floats past. Shell and stone will last well, but everything else has a strictly limited lifespan. Armor seems likely to be designed to be made quickly and easily, and repaired or replaced easily and often. Complex and timeconsuming things (stitched leather, for example) would be expensive luxuries because they are consumables in a way that similar items on dry land are not.

So, I posit:

• Shields. Making a stiff shield might be awkward, but bone and shell might be enough to provide a framework to build upon with some other softer but tougher material... skins or plants. A big turtle shell might be nice, but I can see problems with species being hunted to extinction in the event of protracted warfare.
• Helmets, and possibly pauldrons. Bone and shell again, probably woven together with plants or sinews and onto a harness. Much smaller than shields, so easier to engineer. Smooth and curved as possible to to help keep the wearer streamlined and to help deflect spear/trident tips.

Everything else is probably of increasingly limited usefulness other than looking nice or signifying wealth, if you live in a society where doing such a thing is possible and useful. Your merpeeps are unlikely to be engaging in huge pitched battles (difficult to think of a parallel to an agrarian bronze age for a strictly underwater civilization), but much more likely to be doing raiding for livestock, slaves or plain old theft of shiny stuff. Raiders move fast and light. Slowing yourself down just makes attacking and defending in that sort of environment far harder than it needs to be.

Answer 2

Not Great

It is hard to imagine how whale bones or shells could be fashioned into plates around the body. Seashells are brittle and bones are either flexible when alive or brittle when dead. The shape of a bone is also not suited to making plates.

I suggest the standard armor is a gambeson made of matted kelp. A gambeson is armor made by taking the duvet off your bed and wrapping it around your body.

You might cut through the gambeson with a good sword swing. But you will not cut through the gambeson and chop off the arm underneath. It is even harder if you try sawing back and forth with the sword. Side-note mermaids do a lot of sawing since they cannot swing their swords fast underwater.

Mermaids wear something similar except instead of layers of cotton or linen they use layers of kelp.

The standard armor is made of kelp. But the fancy armor is made of copper. This is either bought or forged by the mermaids on their island forges. Copper is softer than iron but it is good because it does not corrode underwater.

Only a disgustingly wealthy mermaid wears iron armor. Iron armor is disposable armor underwater.