Pressure in the deep

This activity has been designed to help pupils understand the effects of water pressure on animals that live in the deep sea.

To complete the activity, pupils simply need to put a mini marshmallow into a plastic syringe and cover the tip with their finger. Air pressure inside can be decreased by pulling the plunger up, and air pressure can be increased by pushing the plunger down. The marshmallow will expand or shrink depending on how much air pressure it is subjected to.

The marshmallow changes size and shape due to changing air pressure, whereas deep-sea fish change size and shape when subjected to a change in water pressure – for example, when they are pulled up to the surface. This allows pupils to visualise the physical effect of pressure on living creatures, helping them to understand the physical challenges deep-sea creatures face and to consider what adaptations they might need to survive.

This activity is recommended for ages 7 to 12. As the activity involves the dexterity to simultaneously cover the tip of the syringe, hold the syringe in place, and pull the plunger, younger pupils may need a bit of assistance to see the effect.

This resource was created as part of Protecting Our Planet Day (POP) 2023 to highlight the importance of life in the deep sea, and how we explore and protect ocean environments.