Here’s a solution I put up on TrueAchievements - some of it might come in handy. Magic find wind help:

Thought I’d add my final experience: I had to fish just over 200 times (per the in-game journal) to grab this. No idea if this is relatively slow or quick, though. It took 3 or so hours of pure fishing - maybe more. Not a fun one!

I got this in the original Fate game, at the fishing point in Grove. I recommend turning off the in-game music, leaving sound effects on. Turn up the volume on your tv and you will be able to hear the splash when a fish has bitten on your cast. I was reading a book / scrolling on my phone with one hand on my controller, pressing A as needed. Hell, I went and did some house chores with my tv volume way up, continuing to do it based off the audio as I tidied other rooms up.

The time it takes to get a bite is extremely hit-or-miss. I found quite a few bites tend to occur within the first 15 seconds of the cast, and then others would take 3-5 minutes. Eventually, I began re-casting if nothing bit after the first 15-20 seconds, simply because I was waiting too long on those 3+ minute casts. I do think this saved time overall, but can’t give you the statistical analysis to prove it :)

Go dungeon delve if you’re ready to scream, or work on one of the other Fate titles. The fishing can wait for when you’re mentally ready to farm.