A mother who tried to rescue children swept out by an ebbing tide at a shore in Jindo, South Jeolla Province, was found in cardiac arrest together with her three-year-old son, Kyunghyang Shinmun reported on Sept. 12.

The accident happened as the tide was going out. On tidal flats, stretches of strong directional current form during the ebb, and people can be carried off even while standing in shallow water.

Korea's southwestern coast has a large tidal range, so the shoreline shifts markedly through the day. In some stretches the incoming water moves faster than a person can walk.

The coast guard and fire authorities have urged checking tide tables before entering flats and wearing flotation devices, and recommend at least two adults when children are present.

Jumping in to rescue someone in the water often produces a second casualty. Throwing a buoyant object and calling emergency services immediately is the recommended response.

Local governments have installed signage and alarm devices at hazardous stretches, though critics note the limits of oversight on coasts with many access points.

Autumn brings more visitors to the flats for shellfish gathering. Agencies are urging people to check tide information and avoid entering after dark.