You have to do it quickly on the first nibble (not when it goes underwater).

Originally posted by Milmoko:

Anyone else finding this impossible?
The damn fish just eats my earthworms all the time.

I trying reeling in when I feel the pad first vibrate (gets eaten), when the bait dips in the water and it's either too late or to early.

Anyone any tips on when to respond/start to reel in?

As Octopuses said, you have to be quick and, you have to, do it on the first nibble. For this, you will need to use Earthworms. Also, if you think 7 is hard then, good luck with the blue marlins. I know they are irrelevant to this conversation but, I found them to be; much harder to get than the Royal FIsh. For gambit 8, I recommend you use this site, such as this was a big help for me: https://twinfinite.net/2021/04/nier-replicant-blue-marlin-how-get/#:~:text=To%20catch%20Blue%20Marlin%2C%20you,for%20just%2010%20gold%20each.

I'm at the eastern road and using earthworks but when i hit the catch button as soon as the bobber dips a bit the fish just eats my bait...