There _were_ alligators in the river. He almost certainly imagined the gator next to him in the water, but swimming in it was still very dangerous. Gator has

There _were_ alligators in the river. He almost certainly imagined the gator next to him in the water, but swimming in it was still very dangerous. Gator has only one meaning. The protective cloud of pee is just a joke. It's funny because pee is useless to protect you from alligators. It's also funny because peeing yourself is funny.