This time, the lifeguard was at Ocean Beach on Fire Island.
The lifeguard was about 150 to 200 yards out treading water when he or she was bitten.
Officials with the Town of Islip say experts told them it was most likely a sand tiger shark about three to five feet in length.
The lifeguard was bitten around the ankle and only received minor injuries, according to the chief lifeguard of the Ocean Beach District.
Ocean Beach lifeguards also had a fin sighting earlier in the day.
All Fire Island Ocean District will fly purple flags in lifeguard areas and red flags in other bathing areas to signal "dangerous marine life" activity, per the Town of Islip's protocol.
This is the second shark encounter in one week for Suffolk county lifeguards.
A Smith Point beach lifeguard was bitten Sunday during a water rescue training simulation.
MORE NEWS: 'Look at this monster!': Great white shark spotted along Jersey Shore
'Look at this monster!': Great white shark spotted near Sea Ise City, NJ
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