Inkay, the small squid Pokemon, has returned in Pokemon Scarlet and Violet as part of the Indigo Disc DLC, along with its confusing evolution method. This dark/psychic originally appeared on the Nintendo 3DS in Pokemon X and Y with a special method of evolution. In the 3DS version, you had to physically turn your handheld upside in order to get the Pokemon to evolve. This method is similar to how it's done on Nintendo Switch in the Pokemon Scarlet and Violet Indigo Disc DLC, although there are a few additional caveats.
Where to catch Inkay
Inkay is found in the Coastal Biome section of the Terarium, which is the northeastern section of the new area in the Indigo Disc DLC. While they do appear pretty much anywhere in this area, the best places to look are the beaches or in the water itself.
How to evolve Inkay into Malamar
To evolve Inkay into Malamar, Inkay will need to be at least level 30, but all of the ones found in the wild should be over level 50. From there, you will need to level up Inkay to get them to evolve but there are a few special parameters. Inkay will need to level up from battle, not EXP candy. You can use candy to get Inkay close to leveling up, but the final bit of EXP needs to come from a battle against either a trainer or a wild Pokemon. Inkay does not need to do the battling though.