You may have your chemistries confused. There is negligible free lithium metal in LiION cells- there is no risk of the violent reaction with water you seem concerned about. I’m any case if the electrolyte doesn’t leak out of the liPO pouches hkw might you expect water may enter?Just to be clear, P4 batteries are LiPo and they need some special treatment to get the best life span from them. They can be quite dangerous if they are badly treated and can pose quite a fire hazard if they become defective for some reason. I have no experience of problems but there are some horror stories floating around and even a video on YT as I recall. I always charge batteries the day before a flight and store the fully loaded batteries in ammo cans, just to be on the safe side.
The main things to watch out for are visible damage, swelling or contact with water. The LiPo chemicals react violently in contact with water.
This guy is quite a good source of info about many things DJI:
Air crews are trained to use water or any other available beverage liquid (straight spirits likely not advisable) to deal with a liPO fire on board where an extinguisher isn’t readily available.