Hi The long Build,
Do not soak it in water.
It will almost certainly de laminate.
In my experience, most of the early kits I built were not made using waterproof ply.
I could be wrong, but it may ruin what you already have.
I washed the unpainted super structure of a very dusty Sea Commander that I was given, with warm soapy water on a cloth, and it just fell apart.