The priest says, “Oh heavens, I forgot my lures back on land” and steps out of the boat, walks across the water back to the land, and grabs his lures before walking back to the boat.
The atheist was astounded, but before he could make sense of the situation, the rabbi says, “Oh Yahweh help me, I forgot my bait!”
And he also steps out of the boat, and walks across the water back to the land to grab his bait, before walking back to the boat.
The atheist was stunned, but refusing to believe in divinity of any sort or it's impact on the world, he says, “Yeah… I left my extra line on land”.
The atheist hops out of the boat and, “SPLASH!“, he sinks right through to the bottom of the lake.
After a moment the priest looks at the rabbi and says,
“Come to think of it, we probably should have told him where the rocks were.”