Hi
''The impurities in the water causes corrosion and provides circuit paths for the electricity which were not in the phone's operating design and could damage the components. The corrosion starts immediately and is ongoing until it has been properly cleaned away''
First '''do not try to charge or to turn on your phone''' and then '''remove the battery''' as soon as possible to prevent any further damage.
Then you need to dis-assemble the rest of the phone and clean ''all the affected parts'' using '''Isopropyl Alcohol 99%+''' (available from electronics parts stores) to remove all traces of corrosion and water. If possible, do not use "rubbing alcohol" as in some cases this is <70% IPA, can contain additives and is not as effective. If you do have to use it, check the label to verify the amount of IPA
Here is a link that describes the process. [[Electronics Water Damage]]
As always with electronics, especially surface mounted pcb be gentle when handling and especially when brushing away the corrosion. You do not want to remove any components from the boards.
Hopefully after you have done all this the phone ''might'' possibly work correctly again.
Here is the ifixit [[Topic:Samsung Galaxy J3 Luna Pro]] repair guide which may be of some help.
If this process seems too daunting, take your phone to a reputable, professional mobile phone repair service, ''experienced in water damage repair'' and ask for a quote for a repair.
If you decide to do this, ''do it sooner than later''.