Kids and their moms dive into the Shimantogawa river from a submersible bridge in Shimanto, Kochi Prefecture, on Aug. 1. (Masatoshi Kasahara)

SHIMANTO, Kochi Prefecture--Kids dived off a low bridge into the clear Shimantogawa river under a blue sky dotted with thunderclouds in southern Shikoku island.

The day's boiling heat brought packs of elementary school children, junior high school students and families to the Ittohyo bridge, who tried to cool off by jumping into the river.

Some of the kids' moms, perhaps looking to relive their childhood memories of the Japanese summer tradition, took the plunge, too, sending up plumes of water.

The bridge, which is about 61 meters long and 2.5 meters wide, was built in 1935 and is the oldest submersible bridge on the Shimantogawa river.

Low-water bridges, called “chinkabashi” in Japan, are constructed close to the water's surface so they become submerged during floods. Many are built without parapets to prevent them from getting clogged with driftwood.

During summer, the Ittohyo bridge becomes a playground for local children.

The 196-kilometer river is famous for its highly transparent water.

Arata Yamazaki, 12, leapt off the bridge into the river about 2.5 meters below.

“I dived at least 40 times a day,” he said, sporting a fresh tan. “It feels pretty awesome.”

Arata, an elementary school sixth-grader in Shimanto, said he was visiting his grandfather’s house during the summer.

Ami Tamura, 29, brought her 4-year-old daughter, Kanna, to the bridge.

Tamura was one of a group of four moms whose children attend the same local nursery school who came out to the river.

“The Shimantogawa river is so clear,” she said. “The scenery by the bridge is really beautiful.”

Seeing the fun their kids were having shouting and splashing about, they decided to follow them in.

Though a few hesitated when their turn came, they all executed perfect dives, wowing their kids.

“I was a bit scared, but it was lots of fun,” said Shoko Takeda, 33, who used to dive into a river in her childhood.

Locals have set up life-saving equipment including inner tubes and ropes at the foot of the bridge in case of accidents.

Masuo Yamazaki, 72, who makes his living catching fish in the river, installed a ladder against the bridge for safety about 10 years ago.

“Junior high students dive into the river after school. Even adults enjoy doing it,” he said. “I would like to leave this landscape with submersible bridges and the Shimantogawa river for future generations.”