This is a Gyarados EX deck.
Gyarados ex (Scarlet & Violet)
In your opening hand, if you can, put Magikarp on the bench and (preferably) Totodile in the active spot since you can evolve Magikarp into Gyarados EX and Totodile into Crorconaw. Then use Crococnaw's Reverse Thrust attack to deal 30 damage and switch into Gyarados EX.
Using Energy Retrieval and Energy Sticker, you can bring back energy from your discard pile on to your Benched Pokemon or into your hand as this will be vital in order to power Gyarados EX's and Waterfall attack Tyrannical Tail attack.