Hey guys, when I was working on the underwater civilisation challenge i got to thinking what the future arsenal of underwater warfare be like. I'm trying to map an underwater battle around an aquatic colony and want to know what would or wouldn't be feasible/practical underwater weaponry.

I know that ballistic weapons are basically useless underwater, the water provides too much resistance as to greatly reduce weapon range and water pressure on the weapon would prevent spent cases/shells being ejected thus jamming the gun. Weapons like missiles and rockets would useless again because of the extra resistance and because the water would flood their engines prevented them from igniting. Self propelled weapons like torpedoes or using sinking bombs obviously would work but here is a list of futuristic ideas I haven't found a lot of info on in my research. As these weapons would be used by a civilisation that is much more advanced than ours it could be argued that they can find a way around the smaller drawbacks of being underwater so I'm only asking if the technology was advanced enough would the following items THEORETICALLY work or not?

Electromagnetic Weapons (Railguns, coilguns): I know that electromagnetic engines on water vessels are thereoretically possible but what about weapons. If the electromagnets could be properly shielded as not to electrocute anyone close to the damn thing would it work underwater or would a propelled slug have the same drawbacks as ballistic weapons? I also known that electricity loses energy as its forced through water (unless its salt water) if you could create a highly focused "lightning" cannon would it work.

Energey/Beam Weapons: I know lasers can be used underwater and that water refraction does reduce their effectiveness as the beam becomes scattered. Assuming that you could get a good high-yield energy source/generator and could focus the beam to mitigate scatter would beam weapons be plausible, and if so what range would they have?

Sonic/Shockwave Weapons: I have hopes for this one as I know water is great for transferring shockwaves. If you could fire a focused cone of sonic energy or any form of focused directional shockwave what usefulness (if any) would it have underwater.

Magnet bombs: Instead of using electromagnets to propel a projectile could one be used as a weapons, like firing a dormant and very powerful magnet at an enemy ship and activating it to try and cause the metal skin to rip away towards the magnet to create hole breaches or causing ships to implode in on themselves if the magnet activate inside the ship.

Any insight would be most welcomed.