Why are water snakes non-toxic?

In ancient times, one day, the Great Immortal, who was in charge of the five poisons in the sky, ordered all the snakes in the lower world to collect the poisons in the sky.

When the water snake came back with poison, he saw that both the golden ring snake and the silver ring snake were twice poisoned. So the water snake became greedy and wanted a double copy, so he hid one of the general's poisons in cow dung and ran to the sky to ask for another copy. The poison fairy asked the water snake, "You have already received one, why are you still here?" The water snake said, "both the golden ring snake and the silver ring snake accept double poison. I want double poison." The immortal in charge of the five poisons said, "It is true that both bungarus multicinctus and bungarus multicinctus have been poisoned twice, but they are sick for 29 days every month and stay in the cave for 29 days every month, only one day. Will you? " After hearing what he said, the water snake immediately slipped away.

However, when the water snake went to heaven again, the pile of cow dung it was hiding happened to be picked up by an old woman who picked up the dung. So when the water snake came back to get the poison, there was no cow dung. Where is the poison? So since ancient times, water snakes have not been poisonous enough to bite people. However, if you really want to be bitten by a water snake, don't touch cow dung, because once you touch cow dung, the hidden venom of the water snake will attack and the bitten person will be in danger.