Washington’s Blog 
Oct 30, 2012
As we explained earlier today, the Oyster Creek plant in New Jersey is most likely to be affected by Hurricane Sandy .
At around 8:30 p.m. tonight, the U.S. Nuclear Regulatory Commission declared  an “Alert” action level for a nuclear power plant in Oyster Creek, New Jersey:
The U.S. Nuclear Regulatory Commission is continuing to monitor impacts from Hurricane Sandy on nuclear power plants in the Northeastern United States, including an Alert declared at the Oyster Creek nuclear power plant in New Jersey. The plant, currently in a regularly scheduled outage, declared the Alert at approximately 8:45 p.m. EDT due to water exceeding certain high water level criteria in the plant’s water intake structure.
An Alert is the second lowest of four NRC action levels. The Alert was preceded by an Unusual Event, declared at approximately 7 p.m. EDT when the water level first reached a minimum high water level criteria. Water level is rising in the intake structure due to a combination of a rising tide, wind direction and storm surge. It is anticipated water levels will begin to abate within the next several hours.
AP reports: 
The plant’s owner, Exelon Corp., said power was also disrupted in the station’s switchyard, but backup diesel generators were providing stable power, with more than two weeks of fuel on hand.
And Reuters notes :
The NRC spokesman said if the flood waters continued to rise, it could affect the reactor’s service water pumps, which are used for shut-down cooling and to cool the spent-fuel pool.
Since the plant was already shut for refueling, the NRC spokesman said the company could use water from the fire hose to cool the spent-fuel pool if necessary.
See this  for details on the spent fuel pools at Oyster Creek.
Update from Reuters :
Water levels at the plant rose by more than 6.5 feet, potentially affecting the pumps that circulate water through the plant, an NRC spokesman said.
A further rise to 7 feet [only 6 more inches?] could submerge the service water pump motor that is used to cool the water in the spent fuel pool.
The spokesman said the company could use water from a fire hose to cool the pool if necessary. The used uranium rods in the pool could cause the water to boil within 25 hours without additional coolant; in an extreme scenario the rods could overheat, risking the eventual release of radiation.