The correct response is:
When the octopus ejects the water out, the water acts with an equal force on the octopus in the opposite direction.
This illustrates Newton's third law of motion, which states that for every action, there is an equal and opposite reaction. When the octopus pushes the water out of its funnel (action), the water exerts an equal and opposite force on the octopus, propelling it forward (reaction).