Larcoon city, north of Aurora town and south of Kindle Woods and Kindlewood town. A legendary (which was going to be Lugia...) uses some sort of special water move which flooded lower Larcoon and sent a radiation out sending stuff blue.
This is the most complicated map I've made yet, the transparency is so hard to get right and if you change one tile it takes three minutes to change in the water.
Tile credits: Alistair, WesleyFG, Kymotonian, Alucus, Dewitty and I for all pallets and some tiles. If you made anything in this, please tell me.
Update: Changed the tree tops in the water after PrinceLegendario's cc.
Update 2: Fixed trees.
Update 3: Big update this time. Added the route connection, changed some pallets, added people and Pokés and fixed all of the errors.
Update 4: This is the final time Larcoon will be filling your messages, I promise. As now, it's finished! I've added the rest of the map to the east, so you can finally see the whole thing. And I've finally added the steps!