So I've been attempting to get a shiny poliwag, but after 40+ chain I get bored and eventually my reaction slows up and I get "You reeled in to slow,"and I get upset with the game. So I'm asking what are some ways to improve my chances? Will fishing by rocks help in any way? (Yes, I do have a Malmar lvl 35 with Suction Cups) Does running away or fainting the poliwag improve my chances or do they not? If it's not to much to ask answer each question in your response. Thanks in advanced.
This guide explains how consecutive fishing in Pokemon X and Y raises the probability of catching a Shiny Pokemon while fishing for long and uninterrupted periods of time with any rod.
http://www.gamefaqs.com/boards/696959-pokemon-x/67572859
You will always catch a Poliwag if you use an old rod at Route 16. This is because it is a 100% encounter rate when you fish there with an old rod. Poliwag will be at Level 15 so it should be quite easy to actually catch it with a Dive Ball or Net Ball
Running away or causing the Pokemon to faint does not increase your chances of catching a Shiny Pokemon but neither does it decrease them.
I would reccomend Route 14 with Old Rod. Coz the only thing you can catch with Old Rod is Poliwag.
Source :Experience