Engineering design challenge: Water sample

Engineers work to protect the public, and that includes testing their water to make sure it’s safe to swim and play in. Civil & environmental engineers help to complete water testing to look for harmful chemicals and bacteria. They need devices that will hold the sensors for measuring the water at different depths. Some samples need to be taken at the bottom of the riverbed or on the ocean floor; others need to be taken at the surface of the water. There are still others that need to be halfway down, suspended in the water. Engineers need to think about weight and buoyancy of the sensor and its holder, and how to protect it from the elements.

Your mission

Create a water bottle sensor-holder that will be suspended in the water, neither floating to the top nor sinking to the bottom.


You should use objects you can find around the house to build your project (some examples are below).

We recommend that your sensor that your water bottle holds in the middle of the water is a spoon from your cutlery drawer. Figure out a way to attach it to the water bottle that will be reliable even while the sensor is underwater. Think about how to balance out objects that are heavy and sink with objects that are light and float.

Example materials

You can use these or anything else you find around your house to work with

  • Plastic water bottle
  • Metal spoon
  • A basin to test in – a sink, a bathtub, a plastic storage tote or even a large bucket
  • Elastics
  • Tape
  • String
  • Twist ties
  • Nuts, bolts or washers
  • Paperclips
  • Ping pong balls
  • Fishing bobbers

Share some pictures of your creation online using the #NEM2021 or #NEGM2021 hashtag!