Bandırma is a city in Marmara Region, Turkey. It's located on the southern coastline of the Sea of Marmara.
There is a daily train to Izmir via Balikesir.
There are fast ferries several times a day from Istanbul. These ferries also carry vehicles. Get Schedules and Prices here: 
Erdek, and the islands of Marmara and Avsa are nearby resorts.