This activity is presented as a class activity using one Cartesian diver setup, but it can easily be expanded with more materials so that groups of four students or individual students each have an activity setup.

To perform this activity as a class, the following materials are needed:

• 1-liter clear plastic soda bottle with cap, filled with water (soda bottle costs ~$2 or free in recycling bin)
• bowl of water
• Cartesian diver, available at science teaching supply stores, such as the pre-made single Cartesian diver shaped like a squid (#P1-2000) for $2.95 from Arbor Scientific at https://www.arborsci.com/products/single-cartesian-diver
• meter sticks, or other way to measure the classroom dimensions in metric units
• Cartesian Diver Worksheet, one per student
• (optional) if experiencing trouble with squeezing, or to conduct the "Trained Divers" activity extension, use a pressurizing pump to pressurize the 1-liter bottle, such as the individual pressure pumper (#P1-2050) for $3.25 from Arbor Scientific at https://www.arborsci.com/products/individual-pressure-pumper

To have students/groups make their own Cartesian diver setups, each needs:

• 1-liter clear plastic soda bottle with cap, filled with water
• bowl of water
• Cartesian diver, available at science teaching supply stores, such as the pre-made squid-shaped diver described above, or the do-it-yourself super diver kit (#P1-2000-01) with plastic pipettes and other parts and instructions (and a pressure pumper) to make 30 divers from Arbor Scientific at https://www.arborsci.com/products/super-diver-kit; alternatively, obtain your own parts, such as plastic pipettes and weights (nuts, wire), or condiment packets (see below) to make as many divers as you want

How to construct your own Cartesian diver(s) from pipettes, nuts and wire:

• Cut a plastic pipette so that the length of the tube protruding from the bulb is about 1 inch long.
• Place the metal nut around the tube, or wrap some metal wire around the tube to act as a weight.

How to prepare your own condiment packet Cartesian diver(s):

• Ask students to bring to class, or obtain at restaurants or cafeterias, various small plastic condiment packets, such as those for ketchup, mustard, mayonnaise, soy sauce, plum sauce, etc.
• The best Cartesian divers are neutrally buoyant so test the packets in a bowl of water to observe their buoyancy in order to determine which work best as trustworthy divers.