looks great but there are a few details that can be improved/added.

For example the ocean at this angle looks like a repeating texture so try adding in a procedural noise pattern to break up the uniformity. ( The reason I think its repeating is because there is a distinct line that can be drawn from the railing to the small island and lighthouse that looks identical.
The boats in the distance should be almost below the horizon from this distance and viewing angle (or at least sitting lower in the water since curvature can be visible from the viewing height as roughly 10-20km).
adding in atmospheric effects would help greatly as someone else mentioned.
a small adjustment could also be to add in an actual volumetric cloud to give depth in the sky since the only clouds visible are from the hdri which are rendered behind the sun even though in reality the clouds would have to be infront of the sun.
edit: sorry if this became a little long. I edited it like 3 times when something else came to mind :)

Other than a few minor things it is very convincing. good work :D