Forgot to mention ... any passengers bailing out of an IFV or APC whilst in a river/waterway get no saving throws - they are 'toast' like their vehicles.
We've not yet played a game with a mined river or one with anti-tank obstacles in the water ... that would add an extra element of surprize
Paddy fields are classed as marsh/swamp when wet - but remember that most SE Asian rice farms produce 2 crops per year and for a good part of the time under cultivation the rice crop is actually dry.
Fall backs from multiple suppressions do not apply as usual - as an amphibious vehicle will take a go to exit the shore-line (this does not apply to marsh /swamp) - multiple suppressions will effectively destroy the vehicle as if it had to fall back into impenetrable terrain. This may seem harsh but at that point it is on the bank of the river/waterway so the passengers can dice to bail out.
On a beach assault I'd suggest that falling back is far too difficult and the IFV/APC/MBT should effectively fall-back forwards towards the beach and end up supressed on the shoreline and exposed to enemy fire.