It is an old 'truth' that you cannot put out a low voltage fire with water, but it is simply not correct. As long as you keep at least a 1 meter water column between you and the conducting parts, there is no real hazard. This is also a part of the Norwegian DSB's
recomendation (google translate it).
You can also take a look at this dude that testet 110V in hos own sink at way below 1 meter
Hairdryer in Bathtub Myth 3 - bare wires underwater - YouTube.
Electrical flow is all about a having a path or circuit. If the path isn't there, the electricity doesn't flow. So for a battery that is not connected to the ground you are standing on, there is no danger even if the voltage is higher. That is also why the recommendations for putting out ~600v EV battery fires are water. Water it is the only thing that can stop the thermal runaway and in that case you will not get a circuit anyway as long as you do not touche the vehicle at the same time.
I would not hesitate to stand 5 meters away and use a water hose on a 220v fire, not sure about the bathtub test....