The flow of mostly Syrian refugees and migrants braving the seas to seek sanctuary in Europe dipped towards the end of last year coinciding with colder weather, but the total figure still reached 1 million in 2015, nearly five times more than in the previous year.
Seventeen of the bodies were discovered on the shoreline in the district of Ayvalik, while ten others were found in the district of Dikili, a gendarmerie official in the local headquarters told Reuters.
Reuters TV footage showed a body in an orange life jacket lying at the grey water's edge in Ayvalik, lapped by waves. The nationalities of those drowned were not immediately clear.
"We heard a boat sank and hit the rocks. I surmise these people died when they were trying to swim from the rocks. We came here to help as citizens," an unnamed eyewitness said.
Increased policing on Turkey's shores and colder weather conditions have not deterred refugees and migrants from the Middle East, Asia and Africa from embarking on the perilous journey in small, flimsy boats.
The coast guard and gendarmerie rescued 12 people from the sea and the rocks on the Ayvalik coastline. A coast guard official said three boats and a helicopter were searching for any survivors.
In a deal struck at the end of November, Turkey promised to help stem the flow of migrants to Europe in return for cash, visas and renewed talks on joining the EU.
Turkey is host to 2.2 million Syrians and has spent around $8.5 billion on feeding and housing them since the start of the civil war nearly five years ago, but it has been criticised for lacking a longer term integration strategy to give Syrians a future there.
Almost all of the refugees have no legal work status and the majority of children do not go to school.