first thing was to check if those vehicles are really amphibious, using a soap water tub

I'm kidding, and this bath (with warm water, mind you) is intended to dissolve oil, dirt and what not so the model is ready for painting.
oh, and notice that the BTR-50 is sinking, while the PT-76 is actually holding very well



this is a video of HMS sinkhole going down

the models were then let to dry (not in direct sunlight):

