That video (Which lies because there is no FAST way to level fishing, lmao) probably mentioned this, but keep any Level 1 perch you find. You can use these to build a Fishing skill pond, ideally 30M in length by 2 but no more than 4 wide, cast your line and drag it in, fish will nibble, the speed at which they hook is tied to how many fish you catch, so more fish is faster skill, usually you need 20+ Perch in a pond that size to get consistent bites without waiting before you drag to 25m or lower.

Go to about skill level 50 using this method, then I'd recommend going into a new world you don't care about, and sailing to the far north and south to catch the fish in the unfinished biomes, bring these back to your old world and craft the fishing hat with the rest of the fish.

We catch the Northern Salmon and Magmafish in a virgin world so we don't mess up our real world with all our assets and bases on it.