Movie perhaps is product of before 1980. I guess story was in Eastern Europe under USSR power in the Cold War period.
There was a group of young political opponents (3-5 people, maybe one of them a woman) stocked in a concrete basement. They had been said there is a hidden exit. The basement was gradually filled with water and they were going to be drawn and hardly looking for exit. There was no exit, they have been betrayed.
Sorry, I have seen this movie 25 years ago as a child and don't remember more.