Tough Scales is a gear perk that greatly raises your defense against aquatic animals like crocodiles. It lets you swim and fish in dangerous water with less risk.
Attacks from water animals do much less damage. A crocodile ambush becomes something you can fight off.
Wear the Bushwhacker Jeans in the legs 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.
Still Waters stops predators attacking while you fish, and Underwater Adaptation helps you stay under longer.