Beastttt said:
lasers could be tuned to work underwater
At a significant reduction in range yes, limited to several tens of meters maximum, probably only effective at a fraction of that though, perhaps 10 meters.
Beastttt said:
also accelerator rifles snub pistols should work
as they are self powered to work in space
Not because they are meant to "work in space"* but because the rounds are self propelled I agree they would work to a degree.
* (longish rantish

)...
Any modern firearm (by which I mean anything not using a matchlock) will "work in space" presuming you mean a vacuum (or underwater). Air is not needed for guns to go bang. ARs and Snub Pistols are designed to work in zero-g by putting the kick (or most of it) in the round after it leaves the barrel.
In reality the felt recoil of any small firearm is not going to be a problem in zero-g as long as the firer is braced. Even if unbraced there would be no difference in aiming a shotgun or an accelerator rifle, at least for the first shot. And if you have to aim at a different target that action is going to impart more spin on you than the kick from a shotgun.
Zero-g combat is more about knowing how to move, not so much how to manage recoil. Recoil effects can and should be all but ignored for small arms imo, as insignificant (unless you're raised on Hollywood post '50s with all the idiotic gun kick stupidity and insist it's real).
If you have Zero-g skill you can operate normally (you know enough to brace yourself or how to move). If you don't have Zero-g skill it won't matter if you're shooting a 50 caliber rifle or a laser carbine (a true zero recoil weapon in some versions), you will be drifting and tumbling out of control in no time unless you are secured to something. And it won't be due to recoil. If you're secured you're not subject to zero-g penalties.
(end longish rantish, we thank you for your attention, this will be on the final exam... )
In fact low powered weapons like pistols and handguns will work, marginally, underwater without modification. And there have been modified versions of guns that work better. Such as:
http://world.guns.ru/assault/as69-e.htm
I'd also think gauss weapons would work pretty well, though with a range reduction (and/because of needing to reduce the speed) , due to the finned dart projectile being well suited to water.
Beastttt said:
sonic weapons will in effect become grenades as water is a much better conductor of sound
I don't think so. Unless you mean centered on the firing person
Beastttt said:
I'd say rocket launcher will work also
Probably, yes.
Beastttt said:
a shark stick is just a shotgun round on the end of a stick with a special trigger
Yep. But how to model the attack?
Which for all of these seems to be more the answer that rust is looking for. Game stats for underwater combat. He just has to hope it comes in a future supplement I guess. Or make it up himself
