Projectile physics hotfix from Demolitionist.

zscript/utcommon.zsc

@@ -15,6 +15,25 @@ const firstbloodmsg_id = -1401;
 const spreemsg_id = -1402;
 const multimsg_id = -1403;
 
+// backported from DEMOLITIONIST, needed to fix the broken water physics of some projectiles
+Mixin Class UTMissileFix
+{
+	Default
+	{
+		+NOFRICTION;
+	}
+	override void FallAndSink( double grav, double oldfloorz )
+	{
+		if ( bNOGRAVITY || (waterlevel < 1) )
+		{
+			Super.FallAndSink(grav,oldfloorz);
+			return;
+		}
+		vel *= .99;
+		if ( pos.z > floorz ) vel.z -= grav*.01;
+	}
+}
+
 Class UTPlayer : DoomPlayer
 {
 	bool doprintnoammo;
@@ -2149,6 +2168,7 @@ Class UTSpark : Actor
 		+THRUACTORS;
 		+NOTELEPORT;
 		+DONTSPLASH;
+		+NOFRICTION;
 		BounceType "Doom";
 		BounceFactor 0.4;
 		Gravity 0.2;
@@ -2209,6 +2229,8 @@ Class UTViewSpark : UTSpark
 
 Class UTChip : Actor
 {
+	Mixin UTMissileFix;
+
 	int deadtimer;
 	double rollvel, anglevel, pitchvel;