You have to get them to learn the move dive.
teach it to a water Pokemon and search for dark areas in the sea
there hide out under the sea you have to have dive to get there
When you Surf, you will see dark spots in the sea. You can then use Dive, and go underwater.
In the sea, where the water is darker than the surrounding areas.
use dive go in the deep sea grass he will be in the grass
Most water type Pokemon like tentacool.
You have to dive into the sea and go into a tunnel underground and you will find the waterfall there.
You have to use Dive in Sootopolis City and look for it under the sea.
The Braille reads: "DIVE"
you need to be a member to dive into the sea
It is in stormy sea. You'll need the TM Dive, you can get it from Wishcash at the pond.
you have to teach it to a water Pokemon and then go to Pokemon, select the Pokemon you taught it to and you can dive.