Odawarla

Odawarla as seen from space.

Odawarla is the 9th stage station planet on the Galaxy Highway, almost entirely covered by oceans. In the past, its inhabitants all lived underwater, but since then land has been artificially created to allow people to live on the planet as well. As such, Odawarlans, who look like merfolk, have adapted to the new environment too and now also live on land. They breathe using their lungs, but still have their gills – although now atrophied. It is revealed, though, that at least in case of some Odawarlans they can still work as intended with some training.

Artificial land on Odawarla.

Odawarla’s oceans are inhabited by all sort of colourful fishes and sea creatures, at least some of which are used as local food and offered to be self-caught by visiting tourists. One named local speciality is the Odawarla-uo fish. Another marine creature, the Odawarla oarfish, is considered to be so elusive that for offering a fish loaf made of it to the local god one can receive a high monetary reward.

Merfolk of Odawarla.

Not much more is revealed about this planet apart from the fact their medical services and wedding ceremonies appear to be at least superficially similar to those on Earth and that recently there have been labour reforms which left some venues undermanned.
It was visited in episode 4.

Trivia

Odawarla is named after Odawara, which was also a station of the original Tōkaidō and traditionally is known for its production of kamaboko processed fish and stockfish.