Debbie Lockwood of Mercerville, New Jersey tells Action News, "The current in the river is very strong and you get caught in one of them, one of those strong currents, that it pull you right under."
That's exactly what can happen to someone who risks going out on what looks like a completely solid surface.
Officials say the Good Samaritans who rescued Duke the dog, who got stranded out on the ice in Trenton Sunday for hours, were lucky when they managed to return to shore safely.
If the ice breaks and you fall through, Trenton's Deputy Fire Chief Leonard Carmichael says you're flirting with disaster.
Deputy Chief Carmichael says, "Once it sucks you under the ice there's nowhere to get air. You get under and the current is just going to keep pushing you down."
Bob Lockwood fell through the ice when he was 13-years-old.
"Your body goes nuts ... and all you can think of is getting out of the water, and then your pants freeze," Lockwood said.
Today a Coast Guard Cutter was slowly breaking up the chunky ice that's clogging the Delaware River near Trenton.
Matty Kicinski of Port Richmond was one of a number of people who stopped to watch the ice cutter at work.
Kicinski says, "I only remember ever seeing the river like this one other time and that's when my kids were little, and I'm like 73 now."