19 Degrees · classroom sheet · ages 8 to 11

Shark detectives: the warm-water line

Bull sharks like warm water. Scientists have records of 170 bull shark bites in Australia since 1900. Not one happened when the sea was colder than 19°C (66°F).

The line where the sea stays 19°C or warmer for half the year has moved about 215 km (134 miles) south since your grandparents were kids.

Look at the map. The orange line is now. The blue line is 1950 to 1979.

Your mission

Find Sydney on the map. Is Sydney north or south of the orange line?
Draw an arrow on the map to show which way the warm-water line has moved.
Off Sydney, the sea used to be warm enough for bull sharks about 6 months a year. Now it is about 9 months. How many more months is that?
For every person killed by a shark in Australia, about 49 people drown. Which is the bigger danger at the beach?
Draw yourself staying safe at the beach. (Hint: red and yellow flags!)

Words

Sea surface temperature: How warm the top of the sea is.
Estuary: Where a river meets the sea; the water is part fresh, part salty.
Range: Where an animal can live.
Season: The part of the year an animal is in a place.
Marine heatwave: Days when the sea is much warmer than usual.

Teacher notes

Ages 8 to 11 (Australia Years 3–6, US Grades 3–5, UK Years 4–6) · 45–60 minutes · whole class, then pairs

Learning intentions

Living things survive in places where the conditions suit them, including water temperature.
Maps and numbers can show how a place changes over time.

Success criteria

I can find a place on a map and say which side of a line it is on.
I can work out the difference between two numbers from the sheet.
I can explain one way to stay safe at the beach.

Big ideas

Living things depend on the conditions of their habitat. Climate change is shifting those conditions. Maps and simple data show change over time. Staying safe at the beach.

Curriculum links

Australia (v9)	AC9S5U01 (structural features and behaviours that let living things survive in their habitats); AC9S6U01 (how changing physical conditions affect the growth and survival of living things). Mathematics: reading maps and simple data, subtraction.
United States (NGSS)	3-LS4-3 (in a particular habitat some organisms survive well, some less well, and some not at all).
England (National Curriculum)	Key Stage 2 science: Living things and their habitats; Year 6 Evolution and inheritance (how animals are adapted to their environment); geography fieldwork and map skills.
International Baccalaureate	PYP units of inquiry under Sharing the planet (how living things depend on their environment).
Other curricula	New Zealand: Science, Living World and Nature of Science. Canada (Ontario): Grade 4 Habitats and communities. Most primary curricula: habitats, adaptation and reading simple data.
Global goals	UN Sustainable Development Goals 13 (Climate action) and 14 (Life below water); UNESCO Education for Sustainable Development.

Mapped by topic. Check your own syllabus for local codes.

Lesson sequence

Phase	Time	What happens
Engage	5 min	Ask: what makes a beach safe or unsafe? Share ideas.
Explore	15 min	Read the facts and the map together; answer questions 1–2 in pairs.
Explain	10 min	Discuss why some animals live only where the water is warm enough.
Elaborate	15 min	Questions 3–4; compare shark and drowning numbers.
Evaluate	10 min	Draw the safety poster (question 5); share two posters.

Materials

Printed sheet (2 pages; print the teacher notes separately), coloured pencils. Optional: the 19 Degrees page on a projector to show today's sea temperatures.

Differentiation

Support: Read the text aloud, pair readers with non-readers, and give a number line for question 3.
Extension: Use the 19 Degrees page to pick another beach and compare its warm months now and a century ago.

Assessment

Use the answer guide on the next page. Questions 1–3 check map and number skills; question 5 shows understanding of beach safety.

Wellbeing

This topic involves injuries and deaths. Some students may know someone affected by a shark bite or a drowning. Keep the focus on patterns and staying safe, avoid graphic images and news footage, let students step out if they need to, and follow your school's wellbeing procedures. Sharks hold cultural significance for many Indigenous peoples, including Aboriginal and Torres Strait Islander, Māori, Native Hawaiian and other Pacific peoples; if you explore this, use resources developed with or approved by local communities.

Answer guide. 1: Sydney is north of the orange line, so the water there gets warm enough for bull sharks. 2: the arrow points south (down the map). 3: about 3 more months. 4: drowning, by far. 5: swimming between the red and yellow flags, where lifesavers are watching.

Data: Australian Shark-Incident Database (Taronga Conservation Society Australia and Flinders University); HadISST sea temperature (UK Met Office); Pacoureau et al. 2021; Surf Life Saving Australia. From 19 Degrees, free and open source. © 2026 Blake Erickson.