Agreed. However, I don't think that very many people on this board have access to their own private islands (well, maybe Rig Navigator does), so we will have to make do with the locations that we do have access to.
I understand that. I can definitely observe the sunrise across the sea, as I live in Sydney, which is on the east coast of Australia. I'm contemplating where best to observe the sunset, though - the terrain west of here is anything but flat, and it's not like it can be solved by a short journey further west because there's a mountain range just outside the Sydney metropolitan area. If I start driving early enough in the afternoon, I can get to the other side of the mountain range by sunset (it's more than two hours away), where the terrain is flat and not very high above sea level all the way to the horizon, but don't count on it.
Edit: I just realised that such a significant change in longitude would affect the results considerably. I could, of course, compensate for this mathematically if desired. Alternatively, I could head north, where I could perhaps find a flat viewing location at the same longitude as Sydney, but that would be an even longer drive.