Madgikarp, Sheller, & more basic water Pokemon! :)
No
a good rod or super rod
yes
You can catch it almost anywhere, but you need the good rod to catch it.
You catch Barboach using a good rod. He can be found in the areas of the link provided.
super rod
The route right before sunnyshore city you have to catch it with a super or good rod
route 222 (good rod) mainly magikarps
I'm not sure if it's possible to catch Wooper with a good rod, but you can find it in the tall grass in the Great Marsh, which is located in Pastoria City.
Magikarp
Old Rod.
In all the locations you can catch Remoraid, just use the Super Rod reather than the Goody-Goody Good Rod.