Doesn't happen in all water.  I was able to consistently crash it in E1M2 at
the very beginning on the right side where the secret is but not on the left
side.  Also in E2M1 in the large water room where the secret that
has to be shot is.  I was not able to get it to do this in the water in E1M1
where the secret with the 100 health is.  In this case, the player dies (or
looses all ammo in god mode).  After some more testing, it seems to only
happen when near a secret that has to be shot to open.  If the secret has
been opened, it doesn't crash.

Does not matter if the player is in the water or submerged.

Does not matter if god mode and/or notarget is turned on.

When submerged, this is printed
CALL0      1572(?)
   combat.qc : Killed
   combat.qc : T_Damage
   combat.qc : T_RadiusDamage
  weapons.qc : W_FireLightning
   player.qc : player_light1
  weapons.qc : W_Attack
  weapons.qc : W_WeaponFrame
   client.qc : PlayerPostThink
   combat.qc : Killed
NULL function
Host_Error: Program error

When in water but not submerged this is printed
CALL0      1572(?)
   combat.qc : Killed
   combat.qc : T_Damage
   combat.qc : T_RadiusDamage
  weapons.qc : W_FireLightning
   player.qc : player_light2
   combat.qc : Killed

When in water standing on a platform not submerged (like the octagon shape
around the secret in E2M1) it doesn't crash.