Chris
Although Terneuzen itself is best for photography from late morning to mid-afternoon, you don't need to go through the tunnel to the north bank of the Schelde to have the sun behind you in early morning/afternoons. Two good locations for morning photography are Zeedorp, where the end of a mole is close to the shipping channel, and north of Griete (by two wind turbines). Griete is about 15 minutes from the locks at Terneuzen, Zeedorp another 10 minutes.
as Patrick mentioned, Walsoorden (about 20 km to the east) is an excellent spot in the afternoon, either by the harbour entrance or on a mole about 800m to the north.
Hope you have a good trip
regards Simon