Organizers said Saturday the devices have been fitted to ease any fears of competitors before they dive into Sydney Harbor for the 1.5-kilometer swim. That segment will be followed by a 40-kilometer cycle and 10-kilometer run.

Sharks are often seen in the harbor, which has persuaded organizers to utilize technology which emits an electronic signal to repel them.

Engine noise from boats following the swimmers is also expected to keep any sharks away, while a helicopter crew filming the event will also monitor the situation.