Once you have beat Milo in the Turffield Gym in Pokémon Sword and Shield, your next stop will be Hulbury. After a series of conversations, you will be able to enter the stadium and take on the Gym Mission.
Hulbury’s Gym Mission
The Hulbury Gym Mission involves turning off streams of water that will block your path. You can do this by finding and pressing buttons on the colored panels. Each colored panel will stop the water flowing through a grate with the matching color. Once you’ve hit all the panels, there will be nothing blocking your path and you will be able to battle Nessa, the Hulbury Gym Leader.
To access all of these panels, you will need to fight several trainers along the way. Make sure you battle every trainer to unlock all the paths to the different panels and stop the water from flowing. Trainers in Hulbury Gym use the Water-type Pokémon Tympole, Krabby, Corphish, Remoraid, and Chewtle. Nessa has a level 22 Goldeen, a level 23 Arrokuda, and a level 24 Drednaw that she will Dynamax.
The best Pokémon for the Gym
Since every Pokémon in the Hulbury Gym will be mono Water-type or Water/Rock-type, Grass-type Pokémon are the best. You have a few options for Grass-types up to this point. If you chose Grookey as your starter, you can use him. Otherwise, you can catch Gossifleur on Route 3, the route before the mine. You can also catch Oddish, Budew, and Bounsweet in the Rolling Fields section of the Wild Area.
Electric-type Pokémon will also be fine here, although they don’t do quite as well because they don’t resist Water-type moves like Grass-type Pokémon do. You can catch Elektrike or Joltik in the Wild Area or a Yamper on Route 4 after going through the mine if you wish to use an Electric-type.
Make sure to have your Pokémon at least above level 20 before taking on the Gym Mission. Once you beat Hulbury Gym, it will be on to Motostoke to take on the Fire-type Gym of Sword and Shield.