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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.
Water returning to sea
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.
A quiet gap can be misleading
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.
Check before you enter the water
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.
LET’S THINK
A question to explore
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 and diagrams using these sources. Inclusion does not imply review, endorsement or affiliation by the source organisation. Links marked “Japanese” lead to Japanese-language material.
- [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: 2026-09-20 · Sources checked: 2026-09-20 · Editorial policy