Just looking at the rules for damage when firing into water. -2DV per meter for firearms, and -3DV per meter for other weapons. I'm presuming this is before counting hits for the attack roll? Also, wouldn't this be a bit more than what's listed here? I'd probably go with the -3DV for smaller arms per meter, and perhaps a -5DV for larger weapons, and if this reduces the DV to 0, no amount of accuracy is going to help you.

Because, really? Shooting into water isn't really productive, and the bigger the gun, the less likely you'll actually penetrate the water to hit the target.

To get it really right, it'd be very complicated to model for something that doesn't/shouldn't come up very often. I agree that the -2DV per meter for firearms rule is too simplistic, as it denies actual observable benefits to using some calibers over others.

Personally I'd just say that firing into water doesn't work, unless it does. That way hiding in a millimeter of water probably isn't effective but jumping in the ocean probably is.

Otherwise, my thought is you could just treat water as extra ballistic armor. Like +8 for every half meter or so. By three meters you'd be able to soak about 16DV on average.

Mythbusters did a nice bit on this. The bigger the gun, the quicker the bullet gets useless. Older, low-velocity rounds work far better than new, high-speed stuff. 50 cal shots were worthless after a foot or so, while roundballs would go about 6 feet.

The -DV rules probably need to be toughened up to reflect that.

But why worry to much about it. Are you hunting Marrow? It's such an odd rule that I think most GMs would apply an off the cuff modifier before even looking in the book for it. Seems more approprate to be house ruled than a half page rule in a splat book.

Acually, the PCs are heading into the Deep Laguna, and the 'fire into water' thing is going to be an issue pretty soon. I was looking at this in Arsenal, which already devotes a few pages to it. Just tweaking a paragraph would have been fine.

Don't forget probability of ricochets off the surface of the water.

Found part of that experiment on youtube
http://www.youtube.com/watch?v=yvSTuLIjRm8

So yeah, shooting into water with what runners usually carry won't do anything good. Now the question is how realistic you want your game to be?

I like to think a good rule of thumb is, if you can stab it with a sword, you can properly shoot it. (if you are in a boat, and can hit the thing with a sword underwater, you might be able to hit it with a bullet.) otherwise you are getting into iffy territory. now, throw enough explosives into it and you may not have a problem anymore.

... you want to know how to kill something underwater? drop a concussion grenade in the water. instantly liquify any organism within a much larger radius in the water.

I would say the bullet penetrates (7 - DV) meters and loses DV as appropriate.

The effect of the water is inverse to the power. The higher the velocity of the round, the more it breaks up on impact with the water. So if you wanted to try to be accurate you could do something like:
Water gets a cumulative AR of AP + (DV - 4) per meter.

But at my table, if it comes up, I will rule: For firearms, the water has a barrier rating of 20 at 1 meter.

I would hope more runners routinely carry subsonic rounds.

Here's a mathematician's version:

Treat water as a +1 armor for every 1/DV meters under the water the target sits. Use the base DV not the net-hit modified DV. Then reverse the AP (multiply by -1) of the weapon and apply it every meter.

That is, a Light Pistol at DV 6 with AP 0 will grant +6 armor at 1 meter, and a sniper rifle with DV 12 and AP -2 will grant +14 armor at 1 meter. The light pistol would give +12 armor at 2 meters and the sniper rifle would give +28 armor at 2 meters.

Furthermore, flechette weaponry (assuming true flechettes, and not "shot") would have an extra penetrating effect in water -- a DV12 AP +4 shotgun would only give +8 armor at 1 meter and +16 armor at 2 meters, representing the fact that flechettes (long, thin shards) would be somewhat more aquadynamic.

Apply AP to actual armor normally.

This would have the effect of pretty much neutralizing any shot beyond 3 meters, with lighter rounds enjoying a slight benefit. At 2 meters and beyond, pretty much anyone in armor would be (mostly) safe but unarmored targets might still take some damage.

EDIT:

Add this: presume that ammo like Ex-Ex is just ballistic ammo for the purposes of the water (don't give it the extra DV and AP when calculating how much armor the water grants) but still apply it to the target as normal.

Additionally, presume that ammo designed to cause stun damage outright fails in water, so no Stick-n-Shock or gel rounds would be effective.

By fail you mean the Stick n Shock would basically flatten out as it hit the water, but it could still discharge into the immediate area.

I would say the initial meter radius from contact point with the water would have a bit of a pulse to it at 3S(e), but further out would taper off pretty fast with 2nd meter out at 1S(e) basically tickling the senses.

Some aquatic critters like sharks use electrosensitivity to detect things so using it like this could spook off some beasties who might otherwise stick around to take a bite out of someone.

Electricity acts funny in water. In an enclosed space, like a bathtub, SnS might sting, but in relatively open water an electrical discharge on the surface doesn't tend to propagate downward very far.

Also, SnS assumes that its electrical discharge is 100% directed into the body, whereas in the water you'd see it disperse -- actual electricity tends to take paths, but for the sake of modeling this I'd apply the inverse square law. It wouldn't make it very far at all. Seeing damaging levels even at a meter would probably be unlikely.

Electricity tends to disperse in an all around direction in water, but you are right it grounds out pretty fast. Even a full on RL lightning bolt is effectively grounded out at the 6m mark.

Caution: Test results may vary. We do not endorse using tape measures in open waters during thunderstorms.

SnS is normally a 6S(e) so slashed to half for changing to a radius effect but could just as easy to say it would be the initial meter/hex space (not radius) for this effect and say 1S(e) for the 1 meter out mark. Both values are fairly low and would be easily shaken off, but are there to provide the flavour so to speak.

Ah. That is to say that an actual "hit" (that is a successful attack) might grant you the 3S(e), as the round actually makes it really close to you if not touching (due to the water)? Sure, sounds good.

You mean like a stun grenade?

No. I'm specifically talking about gunfire. Explosives are a completely different ball of rubber bands.

Just checking.

Reasonably. I got ticked off recently looking at the quicksand rules from Pathfinder as well. If Mythbusters say 'this can't be done', I'm going to tend to rule in their favour and go with the results they produce.

Do tell.

I don't think it includes 'hits'. Kinda like hardened armour. So after 3 meters through water your assault rifle bullet is useless, no matter how many hits. Based on Mythbusters, though, that 3 meter is vast exageration. After a single foot of water you probably can't punch through a leather jacket with an assault rifle.

I couldn't be bothered t come up with a rule to reflect that, though. If a PC dive a few feet Under water, he,s good and I'd be more concerned about swimming speed and how long he can hold his breath.

They describe quicksand as supersaturated sand (which it is). They then use the tired old trope that for some reason water with a higher density (which quicksand is due to the sand) makes it easier to sink, when such things actually make it easier to float. The Mythbusters looked at this and showed that you don't actually have any risk of being 'sucked down' by quicksand. In fact, you'll float easier in it than you would normally. A good example of this is the Dead Sea - which has a much higher salt content than you'd expect, and because of this, you actually float easier in it than elsewhere.

It's a tired trope. It's been completely debunked. If you want to have quicksand deathtraps in a fantasy setting (or hell, in Shadowrun), you create a magical geographical location which acts closer to what quicksand was thought to do. It isn't that hard.

"Lightning Sand is a geological anomaly. By all normal appearances, lightning sand appears like normal quicksand, but manifests in astral space as well. When something which a strong astral signature (an Essence of 1 or higher) disturbs lightning sand, the sand particles are drawn to the target. The greater the disturbance, the more sand is agitated, and the more draws to the target, adding to the target's weight and causing them to sink. The victim of lightning sand is usually smothered to death by the sand clinging to his body, pulling him under the surface."

Creepy, hits the trope dead on, and fits nicely in Shadowrun or any other fantasy location where you want people to drown in a liquid which is denser than normal.