Right before the crash the water turret was shooting at some "things" that had a healthbar but that I couldn't see. They disappeared after a while. On the third thing in succession the mod crashed.

The mod Water Turret (0.18.5) caused a non-recoverable error.
Please report this error to the mod author.

Error while running event WaterTurret::on_tick (ID 0)
WaterTurret/control.lua:1153:

[ER Global Lock] Forbidden global read:
{key = "enemy"}

stack traceback:
[C]: in function 'error'
WaterTurret/control.lua:1153: in function 'index'
__WaterTurret/control.lua:400: in function 'target_enemy_or_fire'
WaterTurret/control.lua:593: in function <WaterTurret/control.lua:563>

Thanks for the report. I've commented out a lot of code for 0.18.3, and somehow, the definition of "enemy" (which is used in line 400 of control.lua) must have disappeared. The error comes from a code snippet by eradicator which triggers when an undeclared variable is accessed for reading or writing. Commenting out lines 399 and 400 should fix that.

I won't fix this particular bug myself because I'm already working at version 1.0.0 which includes a major rewrite of the code, so this isn't even in my working version anymore. Please fix this locally and wait a bit longer until I can release the next version! :-)

Right before the crash the water turret was shooting at some "things" that had a healthbar but that I couldn't see. They disappeared after a while.

I guess that would be the dummies I use to mark fires. If you want to have a clear look at what happens, you could create a dummy mod with the name "_debug" that contains just info.json. If that mod is active, you will get an insane amount of log spam -- and the fire dummies will be shown as red dots instead of blanks.

Ok, looking forward to 1.0 then :)

Sorry for the delay. Just uploaded!