Nice work! I like the UI and main logo.
I do agree that the gameplay is a bit boring at the moment, so let me just throw some random ideas out here (I'm sure you thought of some of these but didn't have time to implement).
You could make the night hours consume a chunk of your water and food at the start of the next day. You could add in some sort of sanity meter. You could add in random occurrences, like shark attacks and the like, or finding small islands. The concept seems like the game "60 seconds!" which has somewhat similar mechanics but lots of random events that happen. The direction you take at the start doesn't seem to impact the gameplay (or at least I didn't notice), so maybe there's something you could do there. Maybe you have to take time to build fishing/distilling equipment from debris floating by.