This is the English version of the ILS created in Dutch (Drijven en Zinken, groep 5-6).

This lesson is about floating and sinking, and is suitable for age 8-9. Trough the use of a story (message in a bottle, deserted island, designing a raft), and a helping professor, the interest of the pupils will be aroused.
The pupils learn which of the materials wood, brick, styrofoam, and aluminum will float or sink, and if size and weight are of influence. They experiment using the lab 'Density and Buoyancy'.
Besides, they run through the proces of inquiry learning: formulating questions, formulating hypotheses, experimenting, writing down observations, concluding, reflecting. In the end they apply what they've learned through designing a raft (this is also possible via Padlet, there is an option to choose this within the ILS).

There are 2 videos which are in Dutch. You could replace them with videos matching the content.
Video 1: “Heavy materials will sink, light materials will float”. Not quite, think about this: heavy tree trunks float, light paper clips sink. How is this possible?
Video 2: Things with a similar size are not per se similar when it comes to floating or sinking.