Two things have to happen in area 4 for you to be able to fish Gobul out. Number 1: He has to be in the water and Number 2: He has to be unaware of your presence, ie buried in the ground. If you and Gobul are in area 4 and he's not in the water, give him space. He'll most likely go into the water after a bit. After that (and having him paintballed is important for this) go to another area like 2 or 3. If done right (and reason for the paintball being that you won't see the pink dot, but the yellow circle around the area shows he's there, but underground) you should see the yellow circle around area 4, but he is unaware of your presence. Toss the frog in the water, and after a bit, you'll get 4 things: the subquest completed, a free shiny, some free hits, and that awesome mini-cutscene of such a massive fish monster being pulled out of the water, flapping like a fish out of water, all because of a measly fishing pole and a frog.
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