OSTHEER IS DONE WHEN IT'S DONE!
No, i haven't played as the Soviets, but according to a tip that is displayed during a loading screen, the Soviets can't retreat.
Yeah, this is Retreat to Medic Truck button. Personally I hate idea of retreating soivets to MT. Second retreat was given only Brits, because they are really slow and cumbersome. Soviets aren't.
EDIT: Yes and edit the territory make sure the parts which are inside the water are "Null" (black in territory view).