Make a pen in deep, not too deep water, make sure the pen is in the water and not near land or going up to land. Tame a lot of piranha and I mean a lot. It'll be difficult since they come in groups in the wild and can break fish baskets with one to two hits, so becareful. Keep an eye on health and oxygen. But once in the basket they can spoil really quickly so hurry and release in the pen you built earlier. Keep collecting until you think there's a lot to do the damage. Now go into your pen and set all of the piranha on aggressive. Boom piranha pit. Now you can drop players or animals in.
Hate going into the river to get to the other side but piranhas get you? Well, here’s how you get rid of them. First, find and knock out a pelagornis. Then feed some narcotics do kill any predators around. Come back after a while then feed fish meat because pelagornis does not eat raw meat or raw prime meat. When you’ve tamed your pelagornis make the saddle and fly over the water with out touching it and attack the piranhas. These animals are so annoying but with a pelagornis you can one shot it and get some fish meat.