replace misleading Underwater bool with what it really does

OpenRA.Game/GameRules/WeaponInfo.cs

@@ -105,7 +105,7 @@ namespace OpenRA.GameRules
 		public readonly int ROF = 1;
 		public readonly int Burst = 1;
 		public readonly bool Charges = false;
-		public readonly bool Underwater = false;
+		public readonly string Palette = "effect";
 		public readonly string[] ValidTargets = { "Ground", "Water" };
 		public readonly string[] InvalidTargets = { };
 		public readonly int BurstDelay = 5;

OpenRA.Mods.RA/Effects/Bullet.cs

@@ -143,7 +143,7 @@ namespace OpenRA.Mods.RA.Effects
 						yield return r;
 				}
 
-				var palette = wr.Palette(args.Weapon.Underwater ? "shadow" : "effect");
+				var palette = wr.Palette(args.Weapon.Palette);
 				foreach (var r in anim.Render(pos, palette))
 					yield return r;
 			}

OpenRA.Mods.RA/Effects/Missile.cs

@@ -184,7 +184,7 @@ namespace OpenRA.Mods.RA.Effects
 
 			if (!args.SourceActor.World.FogObscures(pos.ToCPos()))
 			{
-				var palette = wr.Palette(args.Weapon.Underwater ? "shadow" : "effect");
+				var palette = wr.Palette(args.Weapon.Palette);
 				foreach (var r in anim.Render(pos, palette))
 					yield return r;
 			}

mods/ra/weapons.yaml

@@ -820,7 +820,7 @@ TorpTube:
 	Range: 9c0
 	Report: TORPEDO1.AUD
 	ValidTargets: Water, Underwater
-	Underwater: yes
+	Palette: shadow
 	Burst: 2
 	BurstDelay: 20
 	Projectile: Missile