Grade Level
Pre-K - 6th grade as a teacher demonstration
4th - 6th grade as an activity that a group of students can make and present to others

Materials
100 feet of rope (available at a hardware store)
Black permanent marker to mark off lengths on the rope
Card stock for name labels (color code groups if desired, e.g. seals blue, sea lions red)
Lamination resource for labels (school machine or local copy store)
Single hole punch for holes in laminated labels
Cable ties to attach labels to the rope (available at a hardware store)
Extension cord storage wheel to store rope or you use a board (available at a hardware store)

Making the Rope
Choose the marine mammals that will be represented on the rope (e.g. Will the rope be just cetaceans or an assortment of marine mammals in your area or the animals that are in the student's reports.) Include the average length of a human or other thing students are familiar with like the length of a school bus. If you're including whales, the end of the rope is the blue whale, the largest animal on earth at 100 feet long. Make labels for each animal with their name and length. Have them laminated and punch a hole in the end of each. Mark off the lengths for each animal on the rope with the black marker and attach the labels. To prevent the labels from slipping thread the cable tie through the strands of the rope. Below are some animal lengths, but there are many other species that could be included.

Using the Rope
This is a versatile demonstration that can be used at any time in a unit on marine mammals. We enjoy using it with students that have some background, so as you pay out the line, the instructor gives clues and the students guess the name on the label. Once extended, younger students enjoy walking next to the rope to count the number of their steps that equal a blue whale's length, if possible, have students lay down head to toe to see how many students equal a blue whale.