Jellyfish sting kills Australian boy

A 7-year-old Australian boy's excruciating death from a box jellyfish sting was preventable, says a stinger expert.

The unnamed boy was bathing in unprotected waters at Wongaling Beach south of Cairns yesterday when he swam into the poisonous jellyfish.

Witnesses said he was dragged screaming from the sea by his grandfather with marks from the toxic tentacles across his body.

Box jellyfish can grow as big as a basketball, have 60 tentacles and enough venom to kill 60 adults.

Ambulance officers administered anti-venom but the boy suffered cardiac arrest and died.

Stinger expert Jamie Seymour said people must learn it is never safe to swim in unprotected tropical waters from November until May.