Cartesian Diver

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In this demonstration, learners observe the effects of density and pressure. A "diver" constructed out of a piece of straw and Blu-Tack will bob inside a bottle filled with water. This highly visual demonstration works best when learners can try moving the diver up and down themselves. This activity can also be related to how animals, like whales, dive in deep waters. This activity guide includes a helpful video that demonstrates each step of the demonstration.

Quick Guide

Preparation Time:
Under 5 minutes

Learning Time:
Under 5 minutes

Estimated Materials Cost:
1 cent - $1 per group of students

Age Range:
Ages 4 - adult

Resource Types:
Activity, Demonstration


Materials List (per group of students)

  • large plastic bottle (~2L) with lid, filled with water
  • glass filled with water (for testing the ‘diver’)
  • straw
  • Blu-Tack
  • scissors


  • Earth and Space Science
    • Earth Structure
      • Oceans and Water
  • Life Sciences
    • Diversity of Life
      • Animals
  • Physical Sciences
    • Motion and Forces
    • Structure and Properties of Matter
      • Volume and Density
  • The Nature of Science
    • The Scientific Process
      • Conducting Investigations

Informal Categories

  • Animals


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



  • All rights reserved, Institute of Physics,