Science // Ocean Life

Tides, Waves & Currents

Know that the ocean has tides (water level rises and falls twice a day, caused mainly by the Moon's gravity), waves (caused by wind), and currents (rivers of water flowing through the ocean that carry warmth and nutrients around the world)

Ages
7 to 9
Type
Concept
Builds on
2 topics
Leads to
1 topic

Quick check

If the learner noticed the water level changing at the beach during the day, could they explain that tides are caused by the Moon's pull, and that the ocean also has waves from wind and currents that flow like underwater rivers?

Ask this to see whether the topic is secure.

Topic // Mastery

What mastery looks like

What a learner can do once this topic is secure.
  • Describe tides as the regular rise and fall of water level, caused by the Moon's gravity
  • Explain that waves are caused by wind blowing across the water surface
  • Describe ocean currents as large flows of water that carry heat and nutrients around the globe

Topic // Map

Where this fits

What to learn first and what this topic opens up, with the reason for each link. Required links come first.
  • RequiredMust come first
  • HelpfulHelps, but not essential

Before this

2 topics
  • What Is the Ocean?Required

    Ocean Life // Ages 5 to 7

    Tides/waves/currents require basic ocean knowledge

  • Coasts & BeachesRequired

    Ocean Life // Ages 5 to 7

    Tides shape coastal habitats; builds on beach/coast concept

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Tides, Waves & Currents

Ages 7 to 9 // Concept

Leads to

1 topic
  • Oceans & ClimateRequired

    Ocean Life // Ages 9 to 11

    Ocean-climate connection builds on knowing about currents and evaporation

Topic // Research-informed

Teaching notes

From the Marble Skill Taxonomy. These notes have not been validated in classrooms, so treat them as a starting point for your own judgement.

The approach

For ages 7–9: the ocean moves in three ways, each with its own main cause — tides (the regular, roughly twice-daily rise and fall of the whole sea, caused mainly by the Moon's gravity), waves (quick surface movement made by wind blowing across the water, where energy travels but the water mostly stays put and bobs), and currents (large, steady flows pushed by steady winds and by differences in water temperature and saltiness, which carry warmth and nutrients — and the water itself — around the globe). The central goal is matching each phenomenon to its main cause and NOT conflating them — especially the classic errors 'the wind causes the tide', 'tides and waves are the same', and 'a wave carries the water forward'. Keep the tide mechanism at the simple 'the Moon pulls the water into a bulge' level; the two-bulge model and full Sun detail come later.

Common misconceptions

  • Conflating the three — e.g. thinking tides and waves are the same thing, or that waves are caused by the Moon.
  • 'A wave carries the water forward across the sea' — not grasping that the energy travels while the water mostly bobs in place.
  • 'Tides are caused by wind' or 'by the Earth spinning only' — missing the Moon's gravity as the main cause.
  • 'Currents are just where it's windy' — not seeing them as sustained global flows carrying heat and nutrients.
  • 'The Sun has nothing to do with tides' / treating tides as irregular rather than a predictable twice-daily rhythm.

Useful representations

  • A Moon–Earth–water bulge diagram showing the tide following the Moon
  • A wave cross-section with a bobbing float showing energy travelling while water stays put
  • A world map of major surface currents with warm/cold colouring and nutrient flow
  • Three cause–effect cards: Moon→tide, wind→wave, flow→current

Teaching practices

  • Teach the three as THREE separate cause–effect stories so they aren't blurred: Moon→tides, wind→waves, big flows→currents.
  • Target the wave misconception directly with a bob-in-place demonstration (a float rises and falls but doesn't travel with the wave) — energy moves, water mostly stays.
  • Model tides with a simple Moon-pulls-a-bulge representation and connect to the regular, predictable twice-daily rhythm children can relate to coastal timing.
  • Show currents as global conveyor paths carrying WARMTH and NUTRIENTS — tie to why some coasts are milder and why nutrient-rich currents teem with life (links to food webs/climate).
  • Use predict-then-check manipulation (change the wind, move the Moon) so causes are felt, not just told.

Activities to try

  1. 1

    Three dials for the sea: drive each cause, see a different effect

    Why it works: Tides, waves and currents are three different movements, each with its own main cause (the Moon for tides, wind for waves, steady winds and temperature/saltiness differences for currents); a wave moves energy while the water mostly stays in place, whereas a current actually transports water, heat and nutrients across the planet.

    1. Spin the Earth under the Moon and watch the ocean bulge stay facing the Moon while a harbour's water rises as it passes under the bulge and falls as it moves away. Real tides keep a predictable clock of about twice a day (roughly every 12½ hours); this simple one-bulge picture shows only one of those high tides.
    2. Turn up a wind control and watch waves grow across the surface while a tethered float lifts and drops in place without travelling along with the wave.
    3. Launch a current across a world map and watch it carry warm/cold colour and drifting nutrient particles across the globe.
    4. After each, state the cause–effect in one sentence: Moon→tide, wind→wave, steady winds and warm/cold, salty water differences→current.
    5. Say in your own words what travels in a wave (energy, while the water mostly stays and bobs) versus what a current carries (heat, nutrients, and even the water itself).
  2. 2

    Tap-to-reveal: three cause–effect stories

    Why it works: Each sea movement has its own clear cause, and the three can be stated as separate cause–effect stories.

    1. Look at three panels — a Moon–Earth–water bulge, a wind-made wave, and a world current map — and tap each cause to reveal 'what makes this happen?'.
    2. On the current map, tap warm and cold flows and name what they carry (heat and nutrients).
    3. Match three cards: Moon→tide, wind→wave, steady winds and warm/cold, salty water differences→current, and read each back as a full sentence.
  3. 3

    Blow across a tray of water: predict, observe, explain

    Why it works: Breath (wind) makes waves, not tides; the tide follows the Moon on a predictable timetable whether it is windy or calm (strong storms can push water a little higher or lower, but they do not make the tide), so wind strength does not tell you the tide state.

    1. With a shallow tray of water, predict what will happen if you blow gently across the surface, and say why.
    2. Blow and observe the ripples/small waves travelling across.
    3. Explain which of the three movements you just made — a tide, a wave, or a current — and decide whether your breath could have caused a real tide.
    4. Discuss the probes: on a still, windless day would there still be a tide? What in the sky is regular enough to set the tide timetable? If the waves are huge, does that tell you whether it's high or low tide?

Science // Ocean Life

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