Weapon design for underwater hand-to-hand combat

Question

Most hand-to-hand weapons are already streamlined for the obvious reason of minimizing air resistance. But would the same design work for underwater warfare?

My story has a character who is exceptionally skilled in fighting in an underwater environment; he has extensively trained underwater and has the ability to control large bodies of water. He is incredibly tall and muscled. He is strong enough to swing swords and other melee weapons despite the water resistance and his signature strategy when fighting is to create a room-sized body of water around his enemies so he has the advantage due to his training. However I am not sure what the design for his personal weapon should be that could be effective in both on land and underwater combat. Would a typical sword work? or would you need a weapon specifically suited to cut through water rather than air.

I also am not sure what material would be best as it would need to be rust proof.

I have an idea which I will put as an answer and feel free to give your thoughts on that design.

Answer 1

He is strong enough to swing swords and other melee weapons despite the water resistance

Swinging stuff underwater is a massive waste of energy, and even if you're hella strong you'll find that you move more slowly than in air, and hit with less force. Defending against an underwater sword-swinger is probably straightforward, especially if you have any kind of armor on.

Thrust, or grab and crush, don't swing. You'll be faster and much more deadly.

Would a typical sword work? or would you need a weapon specifically suited to cut through water rather than air.

A stabbing sword would work, more or less, but given the difficulty in closing distances and the convenience of being able to strike across an air-water boundary, spears and hooks seem like the way to go.

I also am not sure what material would be best as it would need to be rust proof.

There are some lovely modern nitrogen-rich stainless steels that would be great, but in a setting where people are reasonably expected to use swords they seem a bit anachronistic. Regular steels (or even bronze) would be fine, just so long as you work hard to keep them clean and dry between swims, maybe keep them coated in oil or wax between uses and accept the fact that they are going to get corroded sooner or later and not be too precious about them.

his signature strategy when fighting is to create a room-sized body of water around his enemies so he has the advantage due to his training

If someone created a room-sized body of water around me, it wouldn't really matter what they attacked me with, on account of the fact I'd be busy either trying to swim away, or panicking and drowning, and possibly both.

A nice sturdy knife and willingness to engage in a bit of wrestling would seem to be an ideal way to dispatch panicking targets, and even ones who kept their cool are unlikely to be suitably equipped and trained to fight back effectively. If your target is carrying a nice spear and is known to enjoy swimming and free-diving, maybe its best to just shoot him with a bow and save the water-magic for an easier victim.

Answer 2

The force needed to handle a push dagger would rely completely on your hero's arm strength, and would itself barely be influenced by the drag of the water.
It also allows for two-handed fighting styles, and possibly to defend oneself easily against other melee weapons.

Throw in stainless steel for the blade, and an ivory or another non-corrosive material for the handle, and you're all set for your amphibious altercations.

Answer 3

My story has a character who is exceptionally skilled in fighting in an underwater environment;

It's a shark.

he has extensively trained underwater and has the ability to control large bodies of water.

It's a Magical Shark.

He is incredibly tall and muscled.

It's a Magical Great White Shark.

He is strong enough to swing [...] melee weapons despite the water-resistance and his signature strategy when fighting is to create a room-sized body of water around his enemies so he has the advantage due to his training.

Yes, even a Magical Great White Shark (MGWS) has dagger-like teeth. They are perfect for shredding any body to mouth-sized bits when underwater.

However I am not sure what the design for his personal weapon should be that could be effective in both on land and underwater combat.

Dagger-like teeth obviously, because the character is a Magical Great White Shark. That possibly turns into (appears as?) a human just because that makes it much easier to get so close to the one prey that is available in overabundance: Humans.

How do they fight? Well, they charge in on their target with their superior strength and shape while being submerged. Then they open the hatch without lowering their water-resistance too much because excess water is piped out of the gills. Suddenly, the jaws moving at something like 56 km/h bite close around a limb of their targets and lock shut, trapping it. With the huge mass and the superior fins to allow such, the MGWS then thrashes with whatever limb they grabbed in the mouth, shredding it to the bones and likely ripping it out of the socket, and leaving a quickly bleeding out wounded body behind.

Though, if MGWS is large enough, they just chomp on the target twice to kill it, then swallow it whole.

Answer 4

TL;DR

He just water-bends his way through fights.

Long answer

his signature strategy when fighting is to create a room-sized body of water around his enemies

For the above-water fighting part, I'm not sure I understand why this character needs a traditional weapon for combat. If he can instantly create a room-sized body of water, then traditional weapons for close-quarters combat would seem redundant to me.

Depending on the level of control that the character has on the summoned water, then he would have no need for a fighting weapon for fights that start above-water.

Summoned water is controllable.

For example, if they can create the room-sized volume of water in a rapidly lengthening column, then in the open air the enemy gets launched high up into the air and the fall back to the ground does the rest. Or if they're in an enclosed space, the enemy will be crushed into the ceiling.

Summoned water is not controllable

If they have no control over the form of the water once it's created, and it immediately follows real physics, then they have (at least) two options:

1. They summon the water inside the enemy's lungs and they drown;
2. They summon a volume of water - say 1 m³ (equal to 1000 kg or 1 ton) - a few metres above the enemy and when it falls on them it crushes them, as demonstrated by Richard Hammond and a 1-ton car.

Answer 5

Bronze javelin.

http://frazettamuseum.com/product/LITHO-Atlantis.html

The old school. Your buff Atlantean throws a javelin. He throws it inside the water. He throws it outside of the water. He throws it from inside the water to outside the water. He... ok, you get it. Much throwing.

And he looks good throwing it which is part of the appeal. And it is bronze so it is rust proof, and also his favorite javelin is 5000 years old.

Usually one throw is enough. But if he has to fight two enemies the small one gets the javelin and then he wrestles the big one. The even older school.

Answer 6

I think no matter how strong your guy is, you are better off with a thin round weapon than a broad flat one. A sword is less maneuverable in water, it must be swung edge on, and will be strongly guided by its initial trajectory -- the faster it is swung the more constrained it is. Unlike in air it cannot be rotated or easily swung in an arc; in water a flat blade will strongly resist rotation or a change of direction away from the initial plane it is swung in.

A very narrow sharp blade would be more maneuverable; say the width of a pinky.

I would prefer something like a crossbow for underwater use, with round pointed arrows, or spears. Pikes. Stabbers, not slicers. For grappling, just narrow knives, long daggers, would suffice.

I also don't understand how surrounding a person with a "room sized body of water" when underwater is a thing. Aren't they already surrounded by water?

If you meant on land, then where does this water come from? Magic?

If you are already embracing some sort of water magic, then just make the weapons regular melee weapons and say that he magically moves water out of their path so he can manipulate them as if they are in air.

Answer 7

He is incredibly tall and muscled

This already works heavily against him. As you correctly pointed out, the fighting under water is mainly about drag. The larger the surface area of whatever moving under the water, larger the amount of water that needs to be displaced. If for example your fist has a surface area of 1 dm^2 and you wish to punch 1m ahead of you, you will need to displace 10 dm^3 of water or about 10kg of mass.

If we take the results from this paper, the hand of a Olympic level boxer moves on average at about 10mps, if the distance covered during the punch is about a meter we are talking about acceleration of about a 200ms^-2 displacing 10kg of water, this will in effect be a counter force of about 2000N which is quite a way towards the 3400N Olympic level punchers can actually dish out.

In order to limit this drag as much as possible, I would suggest a stabbing weapon of some sort, with a cone leading up to the point to reduce the drag as much as possible. I would suggest a rapier, with a sleeve which would further decrease the drag.

Answer 8

For slashing and stabbing, you're likely to get more fluid resistance from your arm and body than most weapons designed for these purposes. And the more muscles you build to push harder through the drag, the bigger your muscles and the more drag you feel. There may be a point where there's an advantage, but it would require lots of training. Granted, you said your character has a lot of experience and training, but you can reduce your training if you use a weapon and fighting style designed for underwater close-quarters combat.

This will be designed to reduce the drag on every movement as well as the weapons.

Movements

Your body movements will be small to reduce drag and, as a bonus, make it hard for your opponent to know how to react to it as your telegraphing will be significantly reduced. There's variety of ways to do this, but to get a small movement to create a large movement and a large force, you're looking at twisting and rotating your joints, rather than swinging your arm. Sword/fencing and staff fighting have a lot of these movements. Flick your wrist and you slash your sword tip quickly across a couple of feet. Twist your wrist 180 degrees with your hand in dead center and your bo staff essentially covers all 360 degrees of motion to block all kinds of attacks. Grab your staff with both hands extended at shoulder height and you can use one as a pivot point while thrusting one hand out quickly to add power, but a shorter stroke that has little air/fluid resistance.

There's probably dozens or hundreds of examples of minimal movements in a wide variety of martial arts and other fighting styles that allow for minimal effort and maximum movement.

Weapons

The next focus is having a weapon that works with this. A bo staff or sword are pretty good starting points, but you're limited to a small, round weapon to reduce the drag. Any kind of flat weapon will deflect your swing if it's not exactly pointing towards your target. That may be useful at times, to dodge a block, but will require expert training to be able to use the weapon effectively, let alone in "dodging in unexpected ways". It's not impossible, just impractical.

So what you need is something that's symmetrical to a large extent. Any drag force on one "side" of the weapon needs a nearly exact drag force on the other "side" so it moves predictably. A long thin rod with sharp thorns, barbs, or something similar would work. A "sword" that has a cross section more like a +6 pointed star and sharp on all edges could also work, but may be difficult to sharpen. It would also still have to be a small diameter to avoid excessive drag.

Any hilt or hand guard would need to be spherical or a mesh, or it'll create too much drag due to cavitation. A sphere will still cause this, but likely at a lower rate due to the shape allowing the water to form behind it easier than most other shapes. This might be a minor plot point in research of weapons, to find the "perfect" shape of this guard, whether an elongated sphere into more of an ellipsoid or a partial sphere/ellipsoid is better.

And whatever else your weapon has, it needs a sharp tip. Thrusting, jabbing, and slicing with the tip will be major focuses of your fighting style. You might not be able to get close enough to hack at your opponent with the "meat" of the weapon, but a long gash with the tip of a sword or a 1-2" deep puncture can be significantly painful and limit your opponents movements.

Targets

Your aim may not be to dig into the muscles or organs of your opponent, but rather smaller targets, like tendons, ligaments, or arteries close to the skin. If you cut the things that connect muscles to the bone, the muscle becomes ineffective even if it's otherwise uninjured. Cutting an artery will likely cause them to bleed out.

You are basically looking to score on the most vital and longest/hardest to heal parts of the body. This requires accuracy and severe training. Most martial arts and fighting styles focus on this anyway, so that's not far fetched. It's just that your character will want to be exceptionally good at it. This is far more important than having large muscles to be able to swing a broadsword through water. You don't need to decapitate or dismember a person to beat them, that's just overkill, especially in an environment where movement is difficult.

If you opponent can't stand or swim to keep their head above water, or they can't tread water in deep water to maintain their position relative to their opponent due to cutting the Achilles tendon, they can't fight. If they can't hold their weapon because the tendons in their wrist is cut, and they are bleeding out, they can't fight. You don't need a massive sword or a titanic swing to do this kind of damage.

Stab someone in the lung or throat and they'll be breathing water instead of air. An epee, foil, narrow rapier, or similar style sword is nearly perfect for this, minus the large hilts/guards they tend to have.

Answer 9

Long weapons are bad

A lot of answers agree on spears or longer swords in this setting, but in reality, they are perhaps the worst choice you could go with. The longer your weapon, the greater mechanical disadvantage it suffers when trying to maneuver it. A long weapon is like a giant lever. Your hands move just a little bit to make the head of the weapon travel a much longer distance. This means that the effects of drag acting on the distal end of a long weapon are multiplied by your mechanical disadvantage. In the air, this mechanical disadvantage is negligible meaning you can turn your weapon faster this way, in the water, this effect is enough to make long weapons turn noticably slower. Especially more proximal heavy weapons like spears and swords which lack the distal inertia to power through the resistance. This all means means longer swords and spears will be especially easy to block or just plain out maneuver.

Also, because you are floating, how strong you are does not entirely matter unless you get into a grapple. As you maneuver a long weapon, every action has an opposite and equal reaction meaning that it's not just your spear turning, but so are you. The power from any melee attack can be summed up as coming from three basic sources:

1. The speed to which you can accelerate your weapon.
2. Your weapon's inertia. Note, it is inertia and not mass which matters since a distal heavy weapon generally has more inertia for its mass because of its mass distribution.
3. Your ability push your attack through your opponent once contact is made.

In water, you can not accelerate to the same speeds as you can on land. While some answers cite spear fishing to justify a spear, this activity is done from out of the water, and used to hit fish that are only a few cm below the surface. If a fisher man were to try to throw a spear under water the resistance against his arms would make getting enough speed to pierce even a fish more or less impossible. This is why divers in the water often use harpoon guns or boom sticks in lue of actual spears to protect against sharks. If a traditional spear were an effective weapon under water, they would not choose these single use spears over a reusable one.

Aa for inertia, a distal heavy weapon will better punch through the drag of the water, but distal heavy weapons also takes significantly more energy to get moving in the first place; so, they generally become impractical at lengths greater than about 1/2 that of a comparable proximal heavy weapon. In this setting, you can not so much make a distal heavy weapon longer than a proximal heavy one, but you don't need to shorten it by nearly as much to make it useable.

Lastly, in water you can not plant your feet to drive your attacks through your opponent using your body weight. With no ground to plant into, once you make contact, most of your additional force will be lost pushing the two fighters apart instead of punching through.

Because of how these 3 factors work together in water, even the lightest of armor would become adequate to stop any spear or sword attack and most wounds made to exposed flesh would be superficial at best. However, these effects on common land weapons are the exact disadvantages your hydromancer is looking to exploit. So what he needs is weapon that overcomes or minimizes these disadvantages.

Shorter weapons are better

The biggest disadvantage of a shorter weapons on land is that you have to get past an enemy's longer weapon, but since the water makes this relatively easy, the advantages that shorter weapons have start to come into play.

In the water, you don't have anything to brace yourself against to generate a powerful thrust or cut, so you need to grapple an opponent to immobilize 2 opponents relative to one another enough to deliver a particularly deadly strike. Since this puts you in very close quarters, a short thrusting dagger is good because you don't have to worry about your enemy becoming so close that you can't aim your weapon's tip into them.

Another tactic to consider is the use of a short sword that specializes in draw cuts like a scimitar. While a hewing cut is meant to be done at a distance and relies on the speed and inertia of the sword to cut through, a draw cut can be done in very close proximity and at slower speeds since it relies on the action of slicing across a target to "saw" through them. So even a slightly longer blade that would be hard to point into an opponent can still be effective in a grapple if used this way.

Lastly, a distal heavy blade produces more momentum than it produces water resistance; so, when you do swing, something like a hand-axe will better overcome the water resistance.

The best weapon is the kopis

The kopis was an ancient Greek/Etruscan short sword. Like a dagger, it's blade is short enough to thrust with during a grapple (not to be confused with the longer machaira). Like a scimitar, it also has a curved blade making it great for draw-cuts, and like a hand-axe, it is distal heavy meaning it can be swung relatively well in water. On land, this an exceptionally versatile sword, and unlike many other weapons, it remains versatile even when you are in the water.

As for materials, since you are not spending a lot of time in the water, steel is probably still the best since it takes prolonged exposure to water for it to really rust. If you are looking for a specific historically accurate alloy that a kopis may have been made out of, I would suggest Spartan steel. The Spartans discovered manganese steel alloys ~2000 years before it was rediscovered during the industrial revolution. When added to steel in the right proportions, manganese makes steel harder without making it more brittle. Since Spartan steel also had carbon contents up to 0.25%, a high quality Spartan blade would have been considered on the low end of medium carbon steel... not quite as good as most medieval steels in this respect, but still good enough to hold its edge and form very well when you factor in the manganese. The Greek historian Plutarch also wrote about how the Spartans would intentionally quench thier coins in vinegar to rob the iron of the temper suggesting that the Spartans as a culture knew a lot about tempering which is another big factor in steel quality. Tempering makes steel able to be bent and spring back into its original shape. Between these factors, Spartan steel is actually more similar to modern steel than almost anything you will find in the ancient, medieval, or even renaissance periods.

Answer 10

Just a small addition on how to find "spears" or "javelins" that do not rust, take a narwhal tusk.

In that case, the best fighting style underwater would probably differ a lot from land based fights. As pointed out by Dvorkam, swinging your arms around fast underwater make a lot more drag than in the air.

The best strategy probably is to be as narwhal-like as possible, attaching the tusk to himself, and then swimming as fast as possible into his opponents to stab them.

He would have advantages compared to a narwhal, though. The tusks can be carved, for the appropriate weight and length, and also inspire itself from historical spear designs to avoid getting stuck in an opponent. He can also carry several, have them easily detached to himself in case it gets stuck, ...

Answer 11

Evolution has already answered this question for you:

Ramming

Usually a bigger fish thing, they simply swim really fast and use their momentum to do damage. Bonus if you have a sword nose.

Biting

This has an advantage of not needing to build up momentum. Tear a chunk out of the enemy, with no concern for underwater movement speeds.

If you don't want your hero to have a giant shark mouth, then give him a mouth-like weapon to hold in his hands. Something like old-fashioned bear traps that he holds. Then he can just thrust forward and directly place the bitey weapon on the enemy, no aquatic swinging needed.

Answer 12

I would lend my vote to stabbing weapons. Swinging a sword would be complicated by lateral forces due to attack angle through the water. If he can control water, then making a 1" stream go up someone's nose at sufficient speed would almost certainly be fatal. A weapon that may be used against him could be a hypersonic torpedo!

Answer 13

I guess the first question is: where does the water come from, and how much control does your character have over it?

One cubic meter of water weighs a tonne. So in a room large enough to fight in (e.g. 3m tall, 10m wide, 15m long), you'd somehow need to find 450 tonnes of water - or approx 450,000 litres/120,000 US gallons.

That's not just something you can pull out of the moisture content of the air. And if it's being teleported in from somewhere, how goes that work? How long would it take to fill the room?

You'd need a window the size of the room's floor to fill the room with any speed, and pressure to match.

And where does all this water go when it's done?

And (if actually fighting in a room), won't the room collapse immediately due to the weight?

I guess it all comes down to how much hand-waving and magic you want to apply to your story.

TBH, if someone can magically create water and/or water-bend it (to use Avatar terminology), then why not be more clever?

Humans are 60% water - Avatar even touches on this with blood-bending. Why not just stop the enemy's heart from beating?

Why not just teleport water into the enemy's lungs?

Why not just open a portal into the Marina trench - at 16,000 PSI, that gives you four times as much pressure as with a pressure washer. Which might not be enough to cut through steel (water cutters are generally over 50k PSI), but I suspect it'll push back any opponents while stripping their flesh to the bone.

Why not just materialise a small sphere around the enemy's head?

And so on.

Big superpowered fight-fests are fun. But you're generally best off fighting clever, rather than harder. And if you do that, then you don't need hand-to-hand combat, or any other weapons.

Answer 14

2 spears that can be held in one hand and Connect with steel wire.

Basically can stab, throw, swing the connecting rod, and strangle with thin wire.

Throw spears at the same time and use wire to trap enemies in water.