Still Waters is a gear perk that stops predators attacking you while you fish. Crocodiles and other animals can interrupt a catch, and this lets you fish in peace.
Predatory animals leave you alone while you have a line out. You can fish dangerous spots without watching your back.
Wear the Angler's Vest in the chest slot. Gear perks are fixed to the piece of clothing that carries them, so you get this one by wearing that piece, not by unlocking it in a menu.
Primetime Angler and Improved Reel Speed make catches faster, so you can swap a fishing set on for farming runs.