How Lifeguards Confirm Shark Sightings At Island Beaches

Nantucket has seen an unprecedented amount of shark sightings this summer, primarily over the past week with 43 confirmed fin sightings at beaches across the island according to harbormaster Sheila Lucey. Given the uptick in shark sightings, it is a good time to go over the protocol the town takes once a fin sighting is confirmed to be a shark.

It can be difficult to identify the type of shark. On top of that, species such as the basking sun fish are observed and thought to be a shark by beachgoers quite regularly. Nantucket lifeguards are trained to identify shark fins and understand the difference between these two, which is that a shark’s dorsal fin cuts through the water in a straight line and is constantly moving while a shark’s tail fin is also exposed.

Once a shark is sighted, lifeguards determine the size of the shark. If the shark is less than 4 feet in length (sand shark or dogfish) people will not be removed from the water.

Lifeguards will then assess the shark’s behavior. If the shark is feeding, stalking or has otherwise peculiar behavior, a closure is indicated regardless of size.

If a closure is initiated, the closure will be terminated two hours after the last observation of the shark if the shark is inside of the swimming area. If the shark is outside the swimming area, the closure will be terminated one hour after the last observation.

Only confirmed sightings warrant a closure of the beach to water activities and must be made from reliable sources such as lifeguards, ATV operators, and the Nantucket Police and Fire Departments.

People can avoid encounters with sharks by staying out of the water between dusk and dawn, staying in groups whenever possible, not swimming in sight of observed seals, and not venturing too far from shore.

Lifeguards are responsible for educating beachgoers about safety to avoid encountering sharks and other marine mammals. Once a sighting has been confirmed, the lifeguards are taught to do the following things.

- To contact police dispatch on Marine, advise police dispatch which direction the shark is heading, how far off shore it is, and approximate size if known,

- Clear the water on the protected beach and fly a double red flag, proceed to adjacent unprotected beaches and advise the beachgoers and swimmers on those beaches.

- Keep the water clear for one hour if outside the safe swim zone and two hours if inside the zone.

- Check availability of an aerial marine survey team to complete a flyover of the area.



- Contact Police dispatch once the closure has been terminated.