Few things can ruin a day on the water quicker than running into, or over, a partially submerged object.

If the object is big enough - a piece of an old dock, a section of piling - it can punch a hole in the hull. Smaller objects can damage a propeller or shaft.

If you're lucky, you just hear a scary thud that does no damage. And this summer, New Jersey boaters are going to need a lot of luck.

Bay channels, rivers and even near-shore ocean waters along the coast are filled with debris swept into the water by Hurricane Sandy - boats, pieces of houses and docks, patio furniture, even cars. Pieces of the Atlantic City Boardwalk have washed up in Brigantine; other pieces, no doubt, are still in the water. At least one Atlantic County marina had its fuel pumps ripped from a gas dock. They are still out there - somewhere.

"The amount of debris that needs to be removed is mind-boggling," Gov. Chris Christie has said. "Everything you can imagine is sitting in our waterways."

State agencies, a contractor hired by the state and various volunteer groups are all working on cleaning up the debris. But as Paul Harris, the president of the New Jersey Beach Buggy Association, told Associated Press writer Wayne Parry, the group has cleaned up areas only to find more debris in the same place two days later. "There's nothing you can do about it. You can't vacuum the ocean," Harris said.

Exactly. That's what makes this threat unusual and lasting. Debris from Sandy will be fouling coastal waterways for years - lurking just below the surface, being pushed onto marshlands and beaches by the wind and tides, and then refloating back into the water the next time the tide is unusually high.

All of it poses a threat to boaters of every kind. Careful skippers know to keep an eye out for debris - but New Jersey's waterways aren't known for having a preponderance of careful, experienced boaters. So many tourists act like dangerous yahoos on the water - look for one of them to be the first to sink a boat by running into an old section of piling.

Swimmers and surfers, too, will face an increased risk. Area lifeguards will have to be on the alert this summer for large pieces of debris coming through the surf.

Sandy also moved around large amounts of sand. Channels that were navigable last summer may be a lot shallower this summer - and some boaters are going to learn that the hard way.

So come April, when people start putting their boats in the water, Hurricane Sandy will still be a major, ongoing threat six full months after she slammed into New Jersey.

Plan to be careful out there, folks.