The "GSP Saturn" giant oil platform turned back Wednesday after failing to pass under the first bridge on Istanbul's Bosporus Strait.

The platform bearing a Panama flag entered the Bosporus from the Sea of Marmara at 10:45 a.m., where water was added into the vessel to lower it so it could pass under the July 15 Martyrs Bridge.

After working to lower it for nearly five hours, the oil rig turned around and headed back toward the Marmara Sea.

It was later learned that authorities would not allow the oil platform to pass under at night. It will anchor near the mouth of the Marmara Sea and pass through the Bosporus in the coming days.