Ah...Route 763. It will lead you straight to Sinistria when you're ready to head there. Although I must warn you, if you don't have a Pokemon that knows surf, you may have a problem traveling on this route. It's the pure ocean. Blue sea, clear sky, Pokemon Trainers and Pokemon alike. That's how it goes. But be careful while you're traveling. The area has had some storms from time to time. If you are aware of a storm that's coming, do not travel or you may be lost at sea. The Pokemon you will find are quite normal ranging from Lapras, Lanturn, Corsila, Starmie and Sharpedo. But be careful. Gyrados roam the route as well. Up to a challenge against this ferocious dragon?
Good luck, Pokemon Trainers.
Pokemon:
Lapras
Lanturn
Corsila
Starmie
Sharpedo
Gryados