They were bored sitting empty, so they decided to perform some experiments.
The physicist says, “I’m gonna measure the depth of the sea.” He proceeds to dive into the sea, but goes too deep. He gets crushed by the underwater pressure, drowns and dies.
The biologist says, “I’m gonna discover a new species.” He proceeds to dive into the sea, and starts looking here and there. He gets stung by a poisonous octopus, and dies.
The chemist sees all of this happening. He takes out a notebook and writes, “Physicists and biologists are soluble in water.”