A pea is smaller than the other peas in a bag. When it is washed in a strainer it falls through the slots and into the sink where it is promptly washed down the drain. It flows with the water, on and on, until it reaches the ocean, plopping down into the water near a school of fish. The ripples attract the attention of a nearby fish who eats the pea. However, the pea may have been small enough to pass through the strainer but it is not small enough for the fish. The fish chokes on the pea and dies. It floats to the surface where it is picked up and gutted by some passing fisherman. The pea falls from the stomach of the fish onto the floor of the boat. The captain sees the pea and concludes that the deck hand did a poor job cleaning the ship. He yells at the deck hand, this makes the deck hand angry and bitter because he did in fact clean the deck. His anger distracts him and he rigs the sails improperly. The ship sets sail but due to the improper rigging it is blown off course and crashes into a coral reef and sinks. The crew gets away on a life raft. The impact of the ship with the shallow ocean floor generates a small wave that pushes the pea across the ocean to where it finally washes up on the shore of a Californian farm. It sprouts in the dirt and is so successful that it overtakes the whole farm, killing the other crops. In order to make up for lost crops the farmer cultivates the peas and sells them at the market. Another customer at the market is angry that the fisherman he usually buys fish from are not there and is forced to buy peas instead. When he goes to wash the peas in the sink for a meal they are quite small and several fall through the strainer and into the drain.
Here is my sketch of how this causal sketch might work, sorry it's sideways.
