Okay, so I gave capturing a shiny Milotic
fishing on bubble spot on Route 1 to verify some of this stuff. After a lil over 5 hours here is my findings on my successful capture.
1) I had to get a bubble spot fairly quickly,or else my 31/31/31/31/31/31 flawless shiny spread would end up 31/x/x/x/x/x/. Didn't matter whether I got the bubble spot on land or on water, If I didn't get one within around 30 steps and 5 body turnsturnarounds or less my standard flawless seed would change to the latter somehow.
2) Once I found a bubble spot routine of less than 30 steps, to get it to reappear at the same spot, the timing had to be perfect. Route one has 1 moving NPC, but that guy frustrating me to no end. You have to get the right timing because if you are too slow or too fast even on the same route, the same bubble spot did not appear unless I was completely in sync.
This was by far the hardest part.
3) Once I got the hang of the timing and bubble spot came I figured my starting frame like normal. Just got next to the bubble spot and fished in first try, 1 Chatot the 2nd time, 2 chatots 3rd time, 3 chatots 4th time. This was consistent whn I fished on the same bubble spot all the time only if it truly was that same less than 30 steps bubble spot, just like regular surf and normal wild captures. I tried other bubble spots that I got to appear consistantly on other spots after 30 steps, but the pokes that came from them where the 31/x/x/x/x/x spread even though it was still well below the 128 steps it takes to advance seed frame, so here is where I knew it had to be a bubble spot appearing less than 30 steps for me.
4) Once I figured out my starting frame was 118 on fishing captures I compared that to bubble spot captures and noticed that bubble spot was 119. The same nature pattern with Chatot calls was also the same, meaning I could have used either capture method since they both required 21 advancedments to get to the 139 and 140 shiny PID frame for a shiny Milotic respecively.
5) Bam! Did everything one last time and here is the result:
Capture info:
seed: FC4AA3ACA55A515D
standard Seed Frame 1 31/31/31/31/31/31
ID: 19412 SID: 58521
Shiny frame: (Fishing) 139 or (bubble spot) 140
Route taken: Looking North surfing while touching coast near walking NPC on Route 1. 5 steps up, 1st turnaround, 5 steps down, 2nd turnaround, 5 steps up, 3rd turnaround, 5 steps down, 4th turnaround, 3 steps up, and 1 turn left for looking right at bubble spot.
Total: 23 steps with 5 body turns/turnaround
Hope this helps a little bit, and sorry for the long post people ;-)
tl;dr: Fishing bubble spot on route 1 RNG is consistent as long as you find a low step bubble spot and time your step routine/pattern very well because NPC messes the bubble spot from appearing even though you follow same routine. I suggest fishing for a shiny Feebas on Route 1 much easier since that took me 12 minutes to do than 5+ hours for fishing a shiny Milotic on a bubble spot unless you are looking for a challenge :P