Why did people tried to leave Vietnam post-unification?

After the fall of Saigon (South Vietnam capital) in 1975, both North and South Vietnam were unified. This was a major event for both sides of the political parties of Vietnam at the time. With the North coming into power, people who supported the South's regiment including politicians, military officers, even civilians were put under arrest or close observation. The fate of a common South Vietnamese at the time will be confiscation of their belongings and sent to re-education camps. Fearing that this will put their own and family members lives at risk, many people have choose to leave behind everything with their families and start their new life in a different land.