3/4R Why did our boats float, then sink?

Last week, we tested whether our boats floated or sank. All of them floated for at least one minute with no ‘passengers’ (marbles) in them. We then put marbles in the boats to see how many ‘passengers’ they could hold. All boats held between 24 and 97 marbles before they sank, well done!

Testing boats

We now need to think about why they floated and then why they sank, using the knowledge we have learnt so far. What do you think?

WALT: use an online design program to create a poster on why your boat floated.

TIB: good communicators use a range of programs to communicate their message.


  • access the Canva website
  • ‘Log in’ using your email address and password (email = firstname.lastname@education.nsw.gov.au)
  • Select ‘Create a design’ and then the ‘Poster’ option
  • Create a poster to explain why your boat floated when it had no marbles in it. Remember to use the scientific concepts we have learnt about this term.
  • When your poster is finished, select ‘Download’ in the top right corner of the screen and then select ‘PDF: standard’
  • Your poster will download. Open it and then save it in our folder in the Collaboration drive.
  • ‘Sign out’ by clicking the face on the top right of the screen