Nassau County's health department had banned swimming at 14 beaches on Long Island Sound and five on the Atlantic coast.
That was because of the rain of recent days.
Storm water runoff after heavy rains can wash all kinds of things into the water, but health authorities are especially concerned about bacteria from sewage.
The beaches that were closed are listed below.
14 Nassau County North Shore Beaches:
Centre Island Sound
Laurel Hollow Beach
North Hempstead Beach Park
Piping Rock Beach Club
Sea Cliff Village Beach
5 Nassau County South Shore Beaches:
Biltmore Beach Club
Hewlett Point Beach
Island Park Beach
Merrick Estates Civic Association
Philip Healey Beach
For up-to-date recorded information on beach closings and openings, call 516-227-9700.
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