Where to find dive in Pokemon y?

In Pokémon Y, the ability Dive is found in the underwater areas of the Kalos region. You can acquire the Dive HM (HM08) from a character named the Dive Instructor in the Sea Spirit's Den, which is located near Route 21. Once obtained, you can teach it to compatible Pokémon, allowing you to explore underwater locations throughout the game. To use Dive, you need to be in a body of water where it is possible to dive.