When you put your Galaxy S9 into Immersive mode, you can really enjoy the beautiful display Samsung is so famed for. However, you can not always keep it turned on so you still have to deal with the status and navigation bars, which reduce the phone's aspect ratio to that of a standard phone. However, if you want to dig a little deeper, there are ways to finally activate the immersion mode of your S9.
With One UI, Samsung has given up the option to hide the navigation bar of your S9 via a small circular button for gesture-based navigation controls that completely get rid of the bar. However, there is still the status bar you need to look at, and although it's transparent on the splash screen, the status bar often becomes opaque, depending on the app you're currently using.