This is the overworld theme for Sealark, an Oceanic Adventure game being developed by Clairvoire.
"Sealark is about a girl who really likes to fish! She is the last fisherman in the whole world! A world that is flooded, populated by only fish people, and of course, fish. And talking birds too, I guess. The point is that the fishing is really good! Until one day, our hero Dove finds a strange boat, and everything changes."