Hi @roroeow7
As you know water and electronics and electricity are not a good mix.
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.
Rice is good to eat but does not fix the problems caused by corrosion.
Don't Put Your Device in Rice. Here's Why...
First do not turn on your phone and then you need to remove the battery as soon as possible from the phone to minimize further damage.
Then you need to completely dis-assemble the rest of the phone and clean all the affected parts using Isopropyl Alcohol 90%+ (available at electronics parts stores) to remove all traces of corrosion and water. Do not use "rubbing alcohol" as in some cases this is only 70% IPA or less, can contain scents and is not as effective. If you do check the label to verify the amount of IPA
Here is a link to the ifixit guide(s) for repairing your phone.
iPhone SE (1st Generation)
Here are a couple of links that describes the process.
Electronics Water Damage
iPhoneの水濡れ・水没ダメージからの復旧方法
You may have to replace the battery as it is very hard to recover a battery from prolonged 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.
If this process seems too daunting, take your phone to a reputable, professional 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.