freshwater fish, weighing in at 400 pound. could this be the culprit? doesn t have a mouth big enough for the bite mark on his leg. reporter: on our own monster quest we find plenty, admittedly of miniature variety. like these bullman ants. look at the size of it mandibles. delivers the world s most painful insect bite. and fish catcher spiders. think where you put your hands. they re all over the place. reporter: to survive you need to eat. we head to the water to catch our dinner. when suddenly, we notice red eyes glowing a few feet away. before we know it, our guide, samuel, has grabbed the monster with his bare hand and hauled it back on our boat. it s a kayman, a relative of the crocodile. locals eat young caymans like this one. adult caymans have been known to eat the locals. look at the size of his head there. it s so distinctive. this is a black armor.