Walkthrough: Just south of the Aether House is Route 14, the path that leads you the Abandoned Thrifty MegaMart where your next Island Trial awaits. There are plenty of Wild Water Pokemon and Water Trainers found down this coastline.
Frillish
Wild Pokemon:
Surfing (Levels 30-33): Finneon(30%), Tentacruel(30%), Pelipper(20%), Frillish (20%)
Fishing (Levels 10-34): Magikarp(55%), Wishiwashi(40%), Bruxish(5%)
Fishing SOS Pokemon #1 (Levels 10-34): Gyarados, Wishiwashi, Bruxish
Fishing SOS Pokemon #2 (Levels 10-34): Magikarp, Wishiwashi, Bruxish
Fishing Bubble Spots (Levels 10-39): Magikarp(40%), Bruxish(35%), Wishiwashi(25%)
Bubble Spots SOS Pokemon #1 (Levels 10-39): Gyarados, Bruxish, Wishiwashi
Bubble Spots SOS Pokemon #2 (Levels 10-39): Magikarp, Bruxish, Wishiwashi
Trainers:
Veteran Brone - Level 36 Whiscash, Level 36 Honchkrow
Swimmer Keoni - Level 34 Pyukumuku
Fisherman Hisato - Level 34 Feebas, Level 34 Gyarados
Collector Kawika - Level 34 Larvitar
Items:
Destiny Knot - Save Swimmer From Frillish
TM30 - Near Veteran Brone
Max Revive - Eastern Beach
Max Potion - Near Hiker
Ghostium Z - Defeat Acerola's Trial
Dusk Ball - Defeat Acerola's Trial
Grassy Seed - Speak To Reporter With Tapu Bulu In Party
Pearl (Hidden - Daily) - Near Northern Exit
Big Pearl (Hidden) - Near Ramp By Fence