Can you place the subject in the center of the frame? I say yes, you can. According to the Rule of Thirds, this is incorrect. The main subject is supposed to work better when placed along the right or left vertical third or the upper or lower horizontal third. This isn't a rule at all, of course. It's just a guideline. Sometimes centrally placed subjects look great, such as this palm tree I shot in the Dominican Republic. A subject placed in the center of the frame is bold, visually dynamic, and it makes a strong statement. In this photo, I think it would have been better if those distant trees in the upper right section were eliminated (I'll have to do that in Photoshop), but I'm very pleased with the placement of the palm.
Notice that this seascape shot has complete depth of field. That was important. Virtually without exception, landscape or seascape photos require complete depth of field.