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Getting Ready for the Dives

Tamie Dickson
Location: unknown

In this lesson, students will pretend to travel to the island of Ambergris Caye off the coast of Belize. Students will work together to complete the measurements needed for their scuba diving gear in preparation for the dives, and they will solve elapsed time problems.

In this part of the "trip" to Belize, students will be solving elapsed time problems about a trip on a water taxi. As a starting point, seat students with their partners and have them view a map of Belize. A simple internet search should direct you to those maps. You may want to print a map for them or make a transparency. If your students view the maps online, it would be a good idea to bookmark the links due to the long URL addresses. You will also need to find a reliable diving site, which lists diving gear. Be sure to prepare these sites before class.

Distribute the Arriving in Belize activity sheet (each student should have their own). Read the introduction aloud, and explain to students that Ambergris Caye is an island off of the coast of the country of Belize, and that it is a popular place to visit due to its closeness to the barrier reef. Have them find it on the map.

pdficon Arriving in Belize Activity Sheet 

Next, go over the directions carefully with students; they will be working both independently and collaboratively to complete the questions. As students work, circulate and listen to the strategies students are using to calculate elapsed time. Ask questions to check for understanding (see #1 in "Questions for Students" below). You may want to close this portion of the lesson by having students share strategies with the whole class.

For the next portion of the lesson, students will be taking measurements to determine the size of gear they will need. Ask students, "What equipment will you need for the dives?" Have students Think, Pair, and Share, and chart their responses. After allowing students to brainstorm, direct them to diving websites to see if there is other equipment that they did not list.

Distribute copies of the Scuba Gear Rental activity sheet, one per pair. Review the gear names in the table. You may want to have student pairs find each type of gear on the web sites listed above.

pdficon Scuba Gear Rental Activity Sheet 

Before you start, it is important that students understand the following:

  • The difference between inches/yards and centimeters/meters on their rulers, and the notation for feet and inches
  • How to round their measurements [Note: The physical tools in this lesson provide a good opportunity to teach basic rounding skills. If an actual measurement occurs between two numbers on the ruler, the student should choose the number that is closer to the actual measurement.] 
  • What "head circumference" means

Go over the instructions with students, and pass out the rulers and yardsticks. Set up the bathroom scale, and remind students that they can do their measurements in any order (to eliminate wait time at the scale). Circulate as students work to be sure students are choosing the correct tool and using it accurately. Assess students as they work, with questions such as:

  • How did you figure out that you needed to order that particular size?
  • If my shoe size is 7 1/2, what size fins would I need to rent? How do you know?
  • My nephew is going to take a junior scuba class for kids under 8. He is 4'6" and 70 lbs. What size wetsuit should I buy for him? Why?

You may want to have students share their data with the group (however, let them volunteer to share, as some students may be self-conscious in sharing this type of information). Ask students why they have different measurements.

Assessment Options

  1. Have students write a journal entry at the close of this lesson describing what they've learned during the activities (over the last 2 lessons). They may share what they liked, what else they would like to learn, and whether or not they would consider taking a real scuba diving class.
  2. While students are working, circulate throughout the room. Assess students to see if they are able to choose the correct measuring device and use it correctly to get an accurate measurement. Have students demonstrate their method, checking for inconsistencies (e.g., they line up the end of the object correctly at the "0" mark on the ruler and not at the actual end).
  3. Collect student activity sheets and check for misconceptions (e.g., did students mistake centimeters for inches?)


  1. Create a bar graph showing the number of wetsuits for each of the sizes. Let students create questions for their partner to answer using the graph.
  2. Let students set a fair price for each piece of scuba gear, and calculate the total price for their rental equipment.
  3. Move on to the last lesson, Ready to Take the Plunge!

Questions for Students 

1. After students complete the Arriving in Belize City activity sheet: The water taxi should take about 50 minutes. Why do you suppose the time is stated as "about" 50 minutes instead of "exactly" 50 minutes? What factors could affect the length of the trip?

[The exact time cannot be given because the speed of the boat depends on the weather, wind, and number of stops. For example, bad weather or engine trouble could cause delays.]

2. While students are working on the Scuba Gear Rental activity sheet: Which tool, the ruler or tape measure, is most appropriate for measuring the circumference of your head?

[The tape measure is flexible, so this tool would be the better tool for measuring around your head than a ruler.]

3. After completing the Scuba Gear Rental activity sheet: Do you think all dive shops in Belize charge the same prices for the rental gear?

[Answers will vary; if a store charges too much, people may not shop at that store, but some stores may have higher prices because their equipment is nicer.]

Unit Icon
Data Analysis and Probability

Scuba Diving in Belize

Explore various real-world applications of different forms of measurement, including time and distance.

Belize's Barrier Reef

In this lesson, students will view several websites and determine what mathematical ideas and concepts are involved in scuba diving. The emphasis is on using technology to help students gain an understanding of how math is used outside of a school setting.

What Time is it in Belize?

Students will calculate differences in time zones and explore the effects of traveling across time zones.

Preparing for the Trip

In this lesson, students will use various resources to choose travel dates, compare temperatures, estimate and calculate distances to Belize City, and determine the length of their flight in preparation for a "trip" to Belize.

Ready to Take the Plunge!

Students will work in pairs on various measurement problems. They will complete linear conversions, find elapsed time, calculate a percentage, and analyze data from a chart.

Learning Objectives

Students will:

  • Calculate elapsed time.
  • Use measurement tools (ruler, meter stick, tape measure, scale) to perform measurements and determine sizes for their scuba gear rentals.
  • Read and interpret a schedule and table/chart.

NCTM Standards and Expectations

  • Understand such attributes as length, area, weight, volume, and size of angle and select the appropriate attribute.
  • Understand the need for measuring with standard units and become familiar with standard units in the customary and metric systems.
  • Understand that measurements are approximations and how differences in units affect precision.
  • Select and apply appropriate standard units and tools to measure length, area, volume, weight, time,
  • Select and use benchmarks to estimate measurements.

Common Core State Standards – Mathematics

Grade 3, Measurement & Data

  • CCSS.Math.Content.3.MD.A.1
    Tell and write time to the nearest minute and measure time intervals in minutes. Solve word problems involving addition and subtraction of time intervals in minutes, e.g., by representing the problem on a number line diagram.

Grade 3, Measurement & Data

  • CCSS.Math.Content.3.MD.A.2
    Measure and estimate liquid volumes and masses of objects using standard units of grams (g), kilograms (kg), and liters (l). Add, subtract, multiply, or divide to solve one-step word problems involving masses or volumes that are given in the same units, e.g., by using drawings (such as a beaker with a measurement scale) to represent the problem.

Grade 3, Measurement & Data

  • CCSS.Math.Content.3.MD.B.4
    Generate measurement data by measuring lengths using rulers marked with halves and fourths of an inch. Show the data by making a line plot, where the horizontal scale is marked off in appropriate units-- whole numbers, halves, or quarters.

Grade 4, Measurement & Data

  • CCSS.Math.Content.4.MD.A.2
    Use the four operations to solve word problems involving distances, intervals of time, liquid volumes, masses of objects, and money, including problems involving simple fractions or decimals, and problems that require expressing measurements given in a larger unit in terms of a smaller unit. Represent measurement quantities using diagrams such as number line diagrams that feature a measurement scale.

Grade 4, Measurement & Data

  • CCSS.Math.Content.4.MD.A.1
    Know relative sizes of measurement units within one system of units including km, m, cm; kg, g; lb, oz.; l, ml; hr, min, sec. Within a single system of measurement, express measurements in a larger unit in terms of a smaller unit. Record measurement equivalents in a two-column table. For example, know that 1 ft is 12 times as long as 1 in. Express the length of a 4 ft snake as 48 in. Generate a conversion table for feet and inches listing the number pairs (1, 12), (2, 24), (3, 36), ...

Grade 5, Measurement & Data

  • CCSS.Math.Content.5.MD.A.1
    Convert among different-sized standard measurement units within a given measurement system (e.g., convert 5 cm to 0.05 m), and use these conversions in solving multi-step, real world problems.

Common Core State Standards – Practice

  • CCSS.Math.Practice.MP1
    Make sense of problems and persevere in solving them.
  • CCSS.Math.Practice.MP4
    Model with mathematics.
  • CCSS.Math.Practice.MP5
    Use appropriate tools strategically.
  • CCSS.Math.Practice.MP7
    Look for and make use of structure.