First, rinse it out with copious amounts of fresh water then add some vinegar and let it sit for a minute or two. Then rinse again and try to clean the contacts with a q-tip or similar then rinse with some alcohol. If you are lucky it will still fire, if so then no worries. I have seen at least 10 floods like that and 7 of them were fixable.
Good luck
Bill
P.S. I understand that the Z240 is not a camera :blinking:
Another trick I have learned with flooded electronics is to stick them in a bag of dry rice enough to cover the item completely and leave it in there for at least 1 day to help absorb moisture. I have had fairly good luck with this on quite a few occasions. I would also recommend trying to contact Inon and check into a possible service/rebuild.
I have a set of the S-2000 and D-2000 with the same battery compartments and worry about the same issue. I always dunk them in a fresh water bin when available while turned off so if I see any excess bubbles I can catch it right away with the hope of not ruining anything. This isn't guaranteed all time of course as the pressure on the dive may have another effect.
I also flooded my Ikelite 161 battery compartment in Bali a few years ago because I did not perform a dunk test at the shop before heading to the beach.