Dotonbori Dive: What Dangers Lurk Underwater?

1. Why Does the "Dotonbori Dive" Keep Happening? — Background and Latest Trends

Dotonbori is known for its "The Osaka" scenery, characterized by neon signs and reflections on the river centered around Ebisubashi (commonly known as Ebisu Bridge), creating an environment where crowd psychology can easily take hold during celebrations. In September 2025, on the night the Hanshin Tigers clinched the Central League championship, it was reported that at least 29 people jumped into the Dotonbori River (under large-scale security). This is clearly a "dangerous act," and authorities repeatedly call for restraint.Mainichi Shimbun

During such heightened moments, the Osaka Prefectural Police deploy about 1,300 personnel and thoroughly implement measures such as displaying yellow multilingual signs reading "Diving is dangerous" every few meters around Ebisubashi to organize the flow and deter incidents. In the 2003 celebrations, an estimated 5,300 people jumped in, leading to fatal accidents.Asahi Shimbun

2. "Physical" Risks Awaiting Underwater

2-1. Water Depth, Temperature, and Visibility

According to Osaka City, the water depth near Ebisubashi is approximately 3.5m, and in winter, the water temperature can drop below 10°C. Wearing clothes reduces buoyancy, rapidly cools the body, and makes self-rescue difficult due to panic and muscle weakness. At night, visibility is particularly poor, and depending on the angle of entry, there is a heightened risk of head and cervical spine injuries.Osaka City

2-2. Embankment Structure and the "Can't Climb Up" Problem

While the Dotonbori River is being developed into a promenade, there are limited places where one can easily climb up, and the embankment continues at a height out of reach. The Osaka City River Division points out the current situation where they have to install lifebuoys thrown from bridges and the danger of hitting illegally dumped items like bicycles upon entry.J-CAST News

2-3. Low Clearance, Bridges, and Collisions with Vessels

Dotonbori is a tidal river controlled by sluice gates. As indicated by the operational constraints such as the effective width and height of the gates and the draft of 1.3m for vessels, clearance under the bridges is low, and tour boats frequently pass by. Approaching vessels or propellers after entering the water poses a risk of secondary disasters.Osaka CityWater Metropolis OsakaIpponmatsu+1

3. Invisible "Fluid and Structural" Risks

3-1. Tidal Influence and Flow Changes Due to Sluice Operations

The Dotonbori and Higashiyokobori Rivers are tidal rivers affected by tide levels, and sluice operations cause changes in water level and flow speed. The "calm water surface" seen during normal conditions is an illusion, and whirlpools and backflows easily form around bridge piers and confluences, making it easy for even strong swimmers to lose their balance.Osaka City

3-2. Bridge Piers, Embankments, and Underwater Structures

Local currents around bridge piers and reflective waves from embankments cause unexpected lateral flows and entrapment. Additionally, contact with illegally dumped items underwater (such as bicycles) can lead to lacerations, fractures, or entanglement, making it difficult to surface.J-CAST News

4. "Sanitation and Infectious Disease" Risks — Especially Dangerous After Rain

4-1. Combined Sewer Overflow (CSO) and Water Quality Deterioration During Rain

Due to historical reasons, the sewer system in Osaka City has a high proportion of combined sewers, and during short, intense rains, untreated polluted water overflows into rivers, deteriorating water quality. Materials from the Ministry of Land, Infrastructure, Transport and Tourism and Osaka City clearly indicate the increased sanitary risks during rainy weather, despite ongoing CSO countermeasures. Even if the water surface appears clear, recent rainfall can drastically change the situation.Osaka CityOsaka Prefecture Official WebsiteMinistry of Land, Infrastructure, Transport and Tourism

4-2. Bacterial Risks Such as Leptospirosis

Leptospirosis is a zoonotic infection that can be contracted by entering freshwater through small skin wounds or mucous membranes. In Japan, it is often reported from summer to autumn, and the basic prevention is "not entering water unnecessarily" and "avoiding water after floods or rain." Early medical consultation is recommended if symptoms like fever, muscle pain, or conjunctival congestion appear.Infectious Disease Information SiteInfectious Disease Information Center

5. Legal Risks and Social Costs

5-1. Even Without "Explicit Total Prohibition," You Can Be Punished

Osaka City is said to have no ordinance directly prohibiting jumping into the river, but there is a possibility of it leading to public indecency (nudity, etc.), minor offenses (shouting, ignoring warnings, etc.), or obstruction of official duties. Ultimately, it consumes a large amount of emergency and police resources, putting pressure on responses to other urgent matters, which is not a small social cost.Bengo4.comOtonanswer

5-2. Security Measures and Awareness by Authorities

During heightened celebratory moods, measures such as deploying about 1,300 security personnel, multilingual warning signs, and closing promenades and regulating traffic flow are implemented. These are measures to prevent crowd accidents (falls, stampedes) and to curb the chain of jumping.Asahi Shimbun

6. Actual Fatal and Serious Incidents (Representative Examples)

• 2003: During the Hanshin victory celebrations, an estimated 5,300 people jumped in, resulting in fatalities.Asahi Shimbun

• January 2015: A Korean man died after jumping in during the New Year countdown.Global Times

• November 2021: A man in his 20s jumped from Ebisubashi and died (rescuers were also put at risk).Asahi ShimbunMainichi Shimbun

• September 2025: Despite security and deterrence, 29 people jumped in (fortunately, a major accident was avoided).Mainichi Shimbun

7. "Practical Alternative Actions" for Travelers and Residents

1. Absolutely do not jump in

2. Follow the traffic regulations along the river (one-way, no stopping)

3. Avoid approaching the waterside during or after rain (possible water quality deterioration due to CSO)##HTML_TAG