Descartes' Diver

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In this activity, learners explore how changes in fluid pressure affect the buoyancy of a Cartesian diver inside a plastic soda bottle. This guide includes instructions for building a diver out of an eyedropper or Bic Pen. In both instances, learners will observe as the diver floats, sinks, or hovers in response to pressure changes.

Quick Guide

Preparation Time:
Under 5 minutes

Learning Time:
10 to 30 minutes

Estimated Materials Cost:
$1 - $5 per student

Age Range:
Ages 8 - 14

Resource Type:


Materials List (per student)

  • An eyedropper
  • A tall drinking glass
  • Room-temperature water
  • One 2-liter soda bottle with screw-on cap
  • Thin, flat bottle (an empty dish washing liquid or shampoo bottle, for instance) (optional)
  • A Bic™ ballpoint pen with transparent plastic body
  • Pliers
  • A small lump of modeling clay the size of a pea


  • Physical Sciences
    • Motion and Forces
    • States of Matter
      • Liquids
    • Structure and Properties of Matter
      • Mass and Weight
      • Volume and Density
  • The Nature of Science
    • The Scientific Process
      • Conducting Investigations

Informal Categories

  • Toys


To use this activity, learners need to:

  • see
  • touch

Learning styles supported:

  • Involves hands-on or lab activities


This resource is part of:

Access Rights:

  • Free access