you have to get the national dex.
you catch banette at the fight area, resort area or survival area
Go north of Resort area, and south of route 228
you use your super rod in the little lake with the tree in it in the resort area and iv herd that the ruler is just a level 100 magicarp.
If you mean Resort Area, Surfing is Goducks, and magicarps from Lv1 to Lv56
Theres a desert area near the resort area go there and use a Pokemon radar and you might be lucky!
The Resort Area
Your villa is in the resort area
In The Resort Area
you go to the resort area
Yes, you can dig up a waterstone in Pokemon platinum underneath the resort area.
resort area
Route 229 (North of the Resort Area)
it's the eastern most area in the battle area (island east of snowpoint)
you catch banette at the fight area, resort area or survival area
you can get 52 in the Eterna forest and in the resort area
the best Pokemon is a lv100 magikarp
you can find dustox above the resort area in the grass