Materials:
Per team: six drinking straws, tape, scissors (optional), pennies, washers or nails as  weights, a tub of water to float the raft in.

Procedure:
Set the stage: you are on a deserted island with only a few materials. Design and  build a miniature raft using only the materials available. Distribute materials.

Allow time for students to design and construct their rafts. Have  students float their rafts, then put on weights until the raft sinks. Keep a record of how  much weight the raft holds.

Challenge students to redesign the raft using the some quantity of  materials so the raft holds more weight.

Note:
Straws will need to be sealed in order for them to float!