Chain fishing may really warrant a completely separate discussion, but I'll chime in as this is where the discussion is currently located...
I tried out chain fishing on my lunch break today, and caught a shiny Quilfish after about 15 minutes of casting. After another 15 or so, I caught a shiny Dragalge. These both appeared, to me at least, to come from the same chain (I was not given any "no biting" messages). I was fishing while surfing, and facing a non-shiny patch of water that was surrounded by shallow, walk-able water on all sides but the one that I was fishing from. I was using the Super Rod, and I had a fainted Inkay with Suction Cups at the front of my party.
I plan on continuing the chain after work tonight. I'll update with any additional findings.