(CNN) -- Flooding overwhelmed parts of the East Coast Tuesday as a result of Superstorm Sandy.
In Little Ferry, New Jersey, floodwaters were six to eight feet deep, and about 75% of the city was underwater, according to the police chief.
"We have people who were actually on roofs of their homes in certain sections. We needed, actually, boats -- we're still using boats to get people out of the low-lying areas," Chief Ralph Verdi told CNN. "I've been a police officer for 33 years. I've never seen this type of devastation from flooding."
Fourteen miles to the south, in Newark, New Jersey, the city's mayor cautioned residents about the severe flooding.
"There are many, many hazards in the streets. Many downed power lines. Still many flooded areas," Mayor Cory Booker told CNN. "People's safety is still principally important."
Here are five things to keep in mind during flooding:
1. Standing water is potentially dangerous
It may be electrically charged from downed power lines, or contaminated by oil, gasoline or sewage, according to the Federal Emergency Management Agency.
2. So is moving water
Just six inches of shallow moving water can make you fall, according to FEMA. The agency advises walking on firm ground where the water isn't moving -- and using a stick to check how solid your footing is.
3. Flood zones can still be risky after water recedes
FEMA warns roads may erode or weaken after a flood. The weight of a car could make them collapse.
4. Be careful re-entering a flooded home
If you can reach the main power switch from a dry location, go ahead and turn off the electricity. But if you have to wade into floodwaters, the Centers for Disease Control and Prevention advises calling an electrician. Also, the foundation of your home may have weakened, so FEMA warns using extreme caution when you go inside.
5. Stay safe cleaning up
You'll want to wear rubber boots, rubber gloves and goggles to avoid being injured by any sharp objects, such as glass or metal, in floodwaters. Since the water may be filthy, any injuries could lead to infections. The CDC has on its website a list of steps to help flood victims stay safe while cleaning up the inside and outside of their homes.