Parents are being urged to warn their children of the dangers of jumping into harbours and rivers during the holidays.

There's growing concern youngsters are putting themselves at risk jumping off piers, jetties and harbour walls to cool-off during the hot weather.

The hazards include boats manoeuvring in harbours, fast currents and changing depth of water due to tides.

Those who bathe in rivers and streams should be aware of sluices and wiers.

Children may not know the depth of the water they're jumping into, which can be very cold and cause cramps.

Chief coastguard Colin Finney says there are bye-laws to prevent people doing this and his teams are on the lookout for those flouting the rules.