START WITH A QUESTION
If waves come towards the beach, why can water carry you away?
LOOK CLOSELYFind the beach first. Now follow the arrows towards the beach, then the arrows away from it.
This is a simplified illustration of water flow. Real currents change with waves and coastal features. Neither this diagram nor the sea’s appearance can tell you whether a place is safe.
This content has not yet been reviewed by a safety specialist. Follow current official information and instructions at the site.
Water returning to sea
NOTICE THISWhere does the water go after waves bring it in?
Follow the movement of water
WHAT THIS TELLS USWater builds up near the shore. Some of it can flow back out in a concentrated current.
Breaking waves carry water towards the shore. Some of that water can collect and flow back out through a concentrated, strong current. This is a rip current.
The blue-green arrows show water moving towards shore; the brown arrows show water moving offshore. Notice that waves and water currents do not always travel in the same direction.
Go deeper: small differences in water level
Breaking waves slightly raise the water level near shore. Differences in breaking along the beach create differences in water level, driving water sideways and then offshore. Sandbars and structures can influence this pattern. The diagram shows one example, not a shape that every rip current follows.
Sources for this explanation: G1
A quiet gap can be misleading
NOTICE THISDoes a gap in the white water mean a safe place to swim?
Water can move through a gap in the breakers
WHAT THIS TELLS USWater can be moving even where the surface looks quieter.
A rip current may run through a gap where fewer waves are breaking, between areas of white water. That gap can look calmer than its surroundings. Currents can also develop near coastal structures.
Their position and strength can change. Learning the signs does not mean you can choose a safe swimming spot on your own.
Go deeper: what a picture cannot tell you
A photograph shows the surface at one moment. It cannot establish the speed or depth of the water, or how conditions will change. Recognising a possible gap in breaking waves does not qualify you to choose a swimming area yourself.
Check before you enter the water
NOTICE THISWho can you check with before entering the sea?
WHAT THIS TELLS USCheck with a lifeguard together with the adult looking after you.
Check the beach’s opening season and hours, swimming area and lifeguard coverage. On arrival, follow flags, signs and instructions from lifeguards or the beach operator.
If you are carried offshore in a rip current, do not keep trying to swim directly back against it. The Japan Coast Guard describes staying calm and swimming parallel to shore to leave the current, or floating in a comfortable position and waiting for help rather than exhausting yourself. What you can do depends on your swimming ability, strength and the conditions. Read the official guidance linked below.
Go deeper: turn knowledge into preparation
Ask your adult: “Where is swimming allowed today?” and “Where can we find help?” Arrows in these diagrams show water movement. They are not routes for you or a friend to swim.
Sources for this explanation: G2
CONNECT THE PICTURE AND THE WORD
Words to remember
- Rip current
- A concentrated flow of water away from the shore.
- Offshore
- Away from the shore, towards the open water.
- Schematic diagram
- A simplified drawing that explains a particular idea.
CAN YOU EXPLAIN IT IN YOUR OWN WORDS?
Check your understanding
Think first, then open each question to read the explanation. You can look back at the diagrams.
Q1Do the offshore arrows show a swimming route?
Explanation: No. They show water movement. Understanding a diagram is different from deciding what to do at a real beach.
Q2You swam here yesterday. Does that mean you can swim here today?
Explanation: Not necessarily. Check today's conditions, permitted swimming area and lifeguard arrangements.
LET’S THINK
A question to explore further
You spot an area with fewer breaking waves. Is that enough to decide it is safe to swim there?
Show a hint and explanation
No. A rip current can occupy a gap with fewer breaking waves. Currents are difficult to see and can change. Check the beach’s official information and follow local instructions.
Explore together, at home or in class
Hide the arrows and discuss what the picture cannot tell you. Then reveal them. Make two lists: things you can observe, and things you still need to check.
Sources & further reading
We developed our own explanations, diagrams and learning questions using these sources. Inclusion does not imply review or endorsement by the source organisation. Links marked “Japanese” lead to Japanese-language material.
Sources for the added diagrams and explanations
Additional sources checked: 2026-09-21. Numerical diagrams use invented teaching values.
- [G1] US National Weather Service: Rip Current Science ↗Breaking waves, differences in water level and varied rip-current patterns.
- [G2] Japan Coast Guard: precautions at the beach (Japanese) ↗Preparation at Japanese beaches and changing sea conditions.
Original lesson sources
- [1] Japan Coast Guard: precautions at sea (Japanese) ↗Rip currents, basic responses and choosing a swimming beach.
- [2] Japan Lifesaving Association: rip currents (Japanese) ↗How rip currents form and why appearance and conditions can be misleading.
First published: 2026-09-20 · Updated: 2026-09-21 · Original sources checked: 2026-09-20 · Editorial policy