Here is an article (in Danish) from Statens Arkiver (Danish State Archives).

According to the article, approximately 7000 East Germans attempted to flee across the Baltic by boat, and at least 174 of them were killed. More than 4500 were apprehended by East German authorities, while 1000-2000 made it to the West.

The article details a sucessful attempt in 1977 by three young people from East Berlin.

To answer your question, it would have been possible, but not easy.