Wierd uncontrolled rotating PT-76B if you drive skew to the water and meanwhile steering into the water.
You can just control the speed but not really the direction (just a bit) of the steering/rotations and if you try to leave the river any strange steering drive you back into the river and you're trapped there.
Wheeled vehicles don't appear to be affected. It's also possible that it's related to ponds, as the M113 seemed fine in sea water (e.g. on Malden 2035).