Titan Pokémon in Pokémon Scarlet & Violet are typically not that hard to find. They tend to be disproportionately sized as the name 'Titan' would suggest. However, the False Dragon Titan Pokémon found in Casseroya Lake does not exactly follow this norm. To challenge it you'll need to do some hunting. Here's where to find the False Dragon Titan in Pokémon Scarlet & Violet
Where is the False Dragon Titan in Pokémon Scarlet & Violet?
If you head to the small island in Casseroya Lake where your way point indicates, you'll see several Tatsugiri flopping on the shores, but no gigantic, dragon Pokémon. You should also notice that the Tatsugiri on this island all have little speech bubbles. On the southern tip of this island should be an orange Tatsugiri that speaks differently from the others and seems to be saying "Taitaaaan".
When you interact with the orange Tatsugiri, a gigantic Dondozo should swallow the little fish, and initiate a battle with you. The False Dragon Titan fight will have three stages. First you'll battle the Dondozo here on the small island, then he'll swim to the inlet of another island indicated on the map below.
Here you'll fight the Dondozo once more. After defeating it, you'll have to face the final phase, a fight against that little, orange Tatsugiri, the False Dragon Titan who was controlling the Dondozo all along. While Dondozo is strictly a water type Pokémon, Tatsugiri is a dual Dragon and Water-type Pokemon, so plan your type match-ups accordingly.
Looking for info on the other Titan Pokémon in Pokémon Scarlet and Violet? Check out How to beat Orthworm the Lurking Steel Titan in Pokémon Scarlet & Violet or How to beat Paradox Donphan the Quaking Earth Titan in Pokémon Scarlet & Violet here at Pro Game Guides.