Submersion is when the wet moodle increases. So you can test when your Expie is submerged by slowly walking into water until it starts to rise.
The only thing I can think of to solve your problem is to delete your game files and reinstall to see if there is a packet loss problem causing liquids to ignore backpack containers
I still don't understand what bug you are talking about, Liquid containers taking on outside liquids when submerged is clearly intended behavior. I'm not talking about that, I'm being baffled why it's a mechanic in the first place, because it works off an insane assumption that you are putting uncapped bottles into your bags.
I was hoping the developer would read this and either disable the mechanic for now, or add a way to close bottles.
