Wet towels deal more damage

Dipping a towel into a potion, fountain, or some other water source
makes the towel wet.  Hitting with a wet towel deals up to 6 points
of damage, but every hit reduces wetness, as does throwing or applying
the towel.  You can also wish for a moist or wet towel.

src/potion.c

@@ -1933,6 +1933,12 @@ dodip()
         return (1);
     }
 
+    if (potion->otyp == POT_WATER && obj->otyp == TOWEL) {
+        pline_The("towel soaks it up!");
+        /* wetting the towel already done via H2Opotion_dip */
+        goto poof;
+    }
+
     if (is_poisonable(obj)) {
         if (potion->otyp == POT_SICKNESS && !obj->opoisoned) {
             char buf[BUFSZ];