Sink or Float Experiments
Swimmers test which body shapes and breathing make them float or sink – learning how breath and shape affect buoyancy.
- Stages
- Stage 3
- Difficulty
- Developing
- Skills
- Aquatic Breathing, Buoyancy
- Equipment
- None
- Age
- 6–99 years
- Group size
- 1–12 swimmers
- Time
- About 5 minutes
- In a lesson
- Skill Development 1, Skill Development 2
- Shared by
- SwimShare Resource
Safety notes
- Breathing-out experiments should be short; stand to breathe whenever needed.
What it develops
- Breathe out in a controlled way underwater
- Use simple water safety skills
How to run it
- Experiment 1: big breath in, star float – note how you float.
- Experiment 2: breathe out, same star – what changes?
- Experiment 3: pencil shape vs tuck (mushroom) – which floats higher?
- Swimmers report findings and the group agrees the 'rules' of floating.
Teaching cues
- Air in your lungs helps you float.
- Wide shapes are steadier.
- Relax – tense bodies sink.
Make it easier
- Do experiments holding the wall.
- Only experiments 1 and 2.
Make it harder
- Try a vertical float – arms up or arms down?
- Swimmers invent their own experiment.
Common faults
- Swimmers standing up too quickly to notice anything.
Corrections
- Count to five for each experiment before standing.
Assistant / L1 role
- Be the scientist's assistant, recording the results on a whiteboard at the poolside.