Tonbach city is a quaint coastal city. There is a lighthouse and a lifeboat/aquatic research centre by the bay (attached to the third gym). There is also a Pokémart and a Pokémon center.
Read about the battle for the Tide badge with Gym Leader Laraine here.
After the battle, Laraine follows the player out of the gym, inviting them to come diving with her sometime, she tells them to look out for her on Odl y Môr Beach. There are undersea ruins there that she is researching.
After finishing up at the Tonbach city gym, the player spots Daphne enjoying the views. She explains she’s just come via Route 7, an overgrown path that has previously been blocked by a group of basking Muddlug. She recommends you explore Anadl Castle before continuing on, she remembers her father saying something about "an old friend in the graveyard".