Afterwards you have to collect 7 more moons to be able to move onto the next kingdom. All you have to do is defeat one of the Broodal mini bosses – Rango. In Lake kingdom Bowser is after the wedding dress and you can put a stop to his evil plans fairly early in the game. You should know by now that in Super Mario Odyssey you have to finish the main story in the land to be able to access all of its areas.
Unlike some of the larger kingdoms, in Lake there is only a few mandatory moons you need to pick up before you are free to roam the land in full.
Lake Kingdom Power Moon Locations Map (click to enlarge)