The South-eastern suburbs of Melbourne include an area around part of the east coast of Port Phillip Bay.
Although all of Melbourne is an extremely safe city, some of the south-eastern suburbs have a local reputation of having a much higher crime rate than other areas of the city. You should be careful of your belongings, and avoid travel during the night. There should be no issues during the day. The larger suburbs of Frankston and Dandenong seem to be the most notorious.