Water resistance: racing shapes through water

Move different shapes through water with a weight, to compare their speeds, and so how streamlined they are. Compare to the shapes of animals that move through the water.
Science content
Biology: Features, Adaptations of Living Things (K, 1, 3, 7)
Physics: Motion and Forces, Newton’s Laws, Gravity (K, 2, 6)
Lessons activity is in
  • tray of water. 5cm deep or more means the shapes do not bump along the bottom too much
  • two medium binder clips
  • fishing line
  • four small binder clips
  • modelling clay, two different colours (one strip from a dollar store pack for each colour; I find about 10-12g works well so that wider shapes do not bump along the bottom)
  • 2 little bags or pots to hold marbles
  • about 8 marbles

Set up:

Cut a piece of fishing line a little longer than the tray.
Remove one arm (handle) from a mini binder clip, tie one end of the line to its remaining arm, and wrap modelling clay around the body of the binder clip. (Left of first photo.)
Thread the fishing line through the arms of the medium binder clip, then tie the free end to the other mini binder clip.
Attach a little pot to this mini binder clip.
See the first image for the result of these steps. Make two of these for one tray.

Half fill the tray with water, then attach the fishing line/clay unit at one end with its medium binder clip.
Allow the pot of marbles to hang down so that its weight pulls the clay up to the medium binder clip.
See the second image.
Attach the second unit next to the first.


Make two different shapes from two pieces of clay in the same tray.
Pull them both to the end of the tray and release at the same time.
Do several times, to see which shape moves through the water fastest.


In general, in the activity, wider shapes move more slowly than narrower longer "streamlined" shapes.
Compare to fish shapes (an image of fish shapes in silhouette is useful for reference). The fish that can move the fastest (e.g. fish that hunt live prey, like salmon) have longer, narrower shapes than those that do not move as fast (e.g. fish that feed on plants or algae).

Optional: give local fish examples and how their shape is an adaptation for how they eat and move. Examples of British Columbia fish:
herring (streamlined to escape predators - larger fish. eat tiny animals)
salmon (streamlined to swim through fast moving water, escape predators and to catch smaller fish)
sole (not streamlined - do not move fast; flattened to hide from larger fish that eat it. eat worms clams)
sculpin (not streamlined - do not move much; camouflaged to hide from predator fish. eat insects)

Optional: Watch a video showing various fish shapes moving through the water e.g. Planet Earth video of fish in the ocean of various shapes. Try this link:


Visualize using technique in turbulence patterns. Difference between streamlined and non-streamlined shapes.

Grades taught
Gr K
Gr 2
Gr 3
Gr 4
Gr 5