Parts of Atlantic County are under five feet of water and most of Atlantic City is flooded, according to Governor Chris Christie.
There is significant flooding in Cape May and Ocean Counties and several rescues are underway on New Jersey's barrier islands.
At a noon news conference, Governor Christie said everyone who ignored the orders to evacuate made a bad decision and are now putting emergency responders in danger.
"This is not a time to be a show off. This is not a time to be stupid. This is a time to try and save yourself and your family. So for anyone who still has electricity on the barrier islands and can hear this or see it, if you can find a way to get off the barrier islands in the next few hours safely, I would suggest to you that you would because tonight it's going to be significantly worse on the barrier islands than it was last night or during the day so far today," said Christie.
The worst of the flooding is expected Monday night when the heaviest rain moves in just before Hurricane Sandy makes landfall around midnight. It will also be high tide.
"When it comes in tonight, we can't rescue you," said Christie.
Eight hundred people have been evacuated from Atlantic City and are staying in area shelters. But Governor Christie said that only 50% of many towns are evacuated in Atlantic and Ocean Counties.